Spectral Tuning and Adaptation to Different Light Environments of Mysid Visual Pigments

In the present thesis, questions of spectral tuning, the relation of spectral and thermal properties of visual pigments, and evolutionary adaptation to different light environments were addressed using a group of small crustaceans of the genus Mysis as a model. The study was based on microspectrophotometric measurements of visual pigment absorbance spectra, electrophysiological measurements of spectral sensitivities of dark-adapted eyes, and sequencing of the opsin gene retrieved through PCR. The spectral properties were related to the spectral transmission of the respective light environments, as well as to the phylogentic histories of the species. The photoactivation energy (Ea) was estimated from temperature effects on spectral sensitivity in the long-wavelength range, and calculations were made for optimal quantum catch and optimal signal-to-noise ratio in the different light environments. The opsin amino acid sequences of spectrally characterized individuals were compared to find candidate residues for spectral tuning. The general purpose was to clarify to what extent and on what time scale adaptive evolution has driven the functional properties of (mysid) visual pigments towards optimal performance in different light environments. An ultimate goal was to find the molecular mechanisms underlying the spectral tuning and to understand the balance between evolutionary adaptation and molecular constraints. The totally consistent segregation of absorption maxima (λmax) into (shorter-wavelength) marine and (longer-wavelength) freshwater populations suggests that truly adaptive evolution is involved in tuning the visual pigment for optimal performance, driven by selection for high absolute visual sensitivity. On the other hand, the similarity in λmax and opsin sequence between several populations of freshwater M. relicta in spectrally different lakes highlights the limits to adaptation set by evolutionary history and time. A strong inverse correlation between Ea and λmax was found among all visual pigments studied in these respects, including those of M. relicta and 10 species of vertebrate pigments, and this was used to infer thermal noise. The conceptual signal-to-noise ratios thus calculated for pigments with different λmax in the Baltic Sea and Lake Pääjärvi light environments supported the notion that spectral adaptation works towards maximizing the signal-to-noise ratio rather than quantum catch as such. Judged by the shape of absorbance spectra, the visual pigments of all populations of M. relicta and M. salemaai used exclusively the A2 chromophore (3, 4-dehydroretinal). A comparison of amino acid substitutions between M. relicta and M. salemaai indicated that mysid shrimps have a small number of readily available tuning sites to shift between a shorter - and a longer -wavelength opsin. However, phylogenetic history seems to have prevented marine M. relicta from converting back to the (presumably) ancestral opsin form, and thus the more recent reinvention of marine spectral sensitivity has been accomplished by some other novel mechanism, yet to be found

Molecular Tuning of Rhodopsins for High Visual Sensitivity in Different Light Environments : Variation in Absorbance Spectrum and Opsin Sequence within and between Species

Visual pigments of different animal species must have evolved at some stage to match the prevailing light environments, since all visual functions depend on their ability to absorb available photons and transduce the event into a reliable neural signal. There is a large literature on correlation between the light environment and spectral sensitivity between different fish species. However, little work has been done on evolutionary adaptation between separated populations within species. More generally, little is known about the rate of evolutionary adaptation to changing spectral environments. The objective of this thesis is to illuminate the constraints under which the evolutionary tuning of visual pigments works as evident in: scope, tempo, available molecular routes, and signal/noise trade-offs. Aquatic environments offer Nature s own laboratories for research on visual pigment properties, as naturally occurring light environments offer an enormous range of variation in both spectral composition and intensity. The present thesis focuses on the visual pigments that serve dim-light vision in two groups of model species, teleost fishes and mysid crustaceans. The geographical emphasis is in the brackish Baltic Sea area with its well-known postglacial isolation history and its aquatic fauna of both marine and fresh-water origin. The absorbance spectrum of the (single) dim-light visual pigment were recorded by microspectrophotometry (MSP) in single rods of 26 fish species and single rhabdoms of 8 opossum shrimp populations of the genus Mysis inhabiting marine, brackish or freshwater environments. Additionally, spectral sensitivity was determined from six Mysis populations by electroretinogram (ERG) recording. The rod opsin gene was sequenced in individuals of four allopatric populations of the sand goby (Pomatoschistus minutus). Rod opsins of two other goby species were investigated as outgroups for comparison. Rod absorbance spectra of the Baltic subspecies or populations of the primarily marine species herring (Clupea harengus membras), sand goby (P. minutus), and flounder (Platichthys flesus) were long-wavelength-shifted compared to their marine populations. The spectral shifts are consistent with adaptation for improved quantum catch (QC) as well as improved signal-to-noise ratio (SNR) of vision in the Baltic light environment. Since the chromophore of the pigment was pure A1 in all cases, this has apparently been achieved by evolutionary tuning of the opsin visual pigment. By contrast, no opsin-based differences were evident between lake and sea populations of species of fresh-water origin, which can tune their pigment by varying chromophore ratios. A more detailed analysis of differences in absorbance spectra and opsin sequence between and within populations was conducted using the sand goby as model species. Four allopatric populations from the Baltic Sea (B), Swedish west coast (S), English Channel (E), and Adriatic Sea (A) were examined. Rod absorbance spectra, characterized by the wavelength of maximum absorbance (λmax), differed between populations and correlated with differences in the spectral light transmission of the respective water bodies. The greatest λmax shift as well as the greatest opsin sequence difference was between the Baltic and the Adriatic populations. The significant within-population variation of the Baltic λmax values (506-511 nm) was analyzed on the level of individuals and was shown to correlate well with opsin sequence substitutions. The sequences of individuals with λmax at shorter wavelengths were identical to that of the Swedish population, whereas those with λmax at longer wavelengths additionally had substitution F261F/Y in the sixth transmembrane helix of the protein. This substitution (Y261) was also present in the Baltic common gobies and is known to redshift spectra. The tuning mechanism of the long-wavelength type Baltic sand gobies is assumed to be the co-expression of F261 and Y261 in all rods to produce ≈ 5 nm redshift. The polymorphism of the Baltic sand goby population possibly indicates ambiguous selection pressures in the Baltic Sea. The visual pigments of all lake populations of the opossum shrimp (Mysis relicta) were red-shifted by 25 nm compared with all Baltic Sea populations. This is calculated to confer a significant advantage in both QC and SNR in many humus-rich lakes with reddish water. Since only A2 chromophore was present, the differences obviously reflect evolutionary tuning of the visual protein, the opsin. The changes have occurred within the ca. 9000 years that the lakes have been isolated from the Sea after the most recent glaciation. At present, it seems that the mechanism explaining the spectral differences between lake and sea populations is not an amino acid substitution at any other conventional tuning site, but the mechanism is yet to be found.

Shooting from the Wild Zone : A Study of the Chicana Art Photographers Laura Aguilar, Celia Álvarez Muñoz, Delilah Montoya, and Kathy Vargas

The dissertation analyzes and elaborates upon the changing map of U.S. ethno-racial formation from the vantage point of North American Studies, multi-disciplinary cultural studies, and the criticism of visual culture. The focus is on four contemporary Mexican American (Chicana) women photographers, whose art production is discussed, on the one hand, in the context of the Euro-American history of photographic genres and, on the other hand, in the context of so-called decolonizing cultural and academic discourses produced by Mexican Americans themselves. The manuscript consists of two parts. Part I outlines the theoretical and methodological domain of the study, positioning it in the interstices of American studies, European postmodern criticism, postcolonial feminist theory, and the theories of visual culture, particularly of art photography. In addition, the main issues and paradigms of Chicano Studies (Mexican American ethnic studies) are introduced. Part II consists of seven essays, each of which discusses rather independently a particular photographic work or a series of photographs, formulating and defending arguments about their meaning, position in the history of photographic genres, and their cultural and socio-political significance. The study closes with a discussion about ethno-racial identity formation and the role of Chicana photography therein - in embodying and reproducing new subjectivities, alternative categories of knowledge, and open ended historical narratives. It is argued that, symbolically, the "Wild Zone" of gendered and race-specific knowledge becomes associated with the body of the mother, a recurrent image in Chicana art works under discussion. Embedded in this image, the construction of an alternative notion of a family thus articulates the parameters of a matrifocal ethno-racial community unified by the proliferation of differences rather than by conformities typical of nationalistic ideologies. While focusing on art photography, the study as a whole simultaneously constructs, from a European vantage point, a "thick" description of Mexican American history, identities, communities, cultural practices, and self-representations about which very little is known in Finland.

Halun häilyvät rajat : Magnus Enckellin maalausten maskuliinisuuksien ja feminiinisyyksien representaatioista ja itsen luomisesta

My PhD-thesis The uneasy borders of desire Magnus Enckell's representations of masculinities and femininities and the question how to create the self concentrates on the works of Finnish fin-de-siècle artist Magnus Enckell (1870-1925). My thesis deals with representations of masculinities, femininities, sexualities and different identity-positions. My research is about questions concerning representational ways of melancholy, androgyny, narcissism, themes of Golden Age and Double in Enckell s ouvre. These themes are analyzed by contextualizing them with different, but intersecting, discourses of varied scientific, artistic and occult ideas in the fin-de-siècle. The main point is analyze how the subject is constructed in both Foucauldian and Freudian sense and what one has to know about oneself. My approaches are based on ideas expressed in different discourses as queer-theory, Michel Foucault s genealogical epistemology and knowledge-power theory, psychoanalysis, art history and visual culture studies. My starting point lays is Foucault s idea expressed in his The History of Sexuality that the constitution of homosexual or as well as heterosexual subject inaugurates possibilities for transgressive activities e.g. by giving own voice to the sexualized subject. My main thesis is to suggest that Enckell s works in their multiple and ambiguous ways construct a phantasmatic position for viewer who may identify oneself to different desires, may construct or deconstruct a sexual identity for oneself or try to define the truth about oneself. Enckell s works should be considered as a contradictory processes which both seduce person to construct an identity and as well as lure person to pursue for the deconstruction of specific and permanent identity by celebrating the ambiguousness and discontinuity in one s identity. I m suggesting that the gazing subject feels pleasure in finding one s identity but the one must face the exposure of the melancholic structure which forms the basis of sexual desire. The subject may try to resolve one s melancholy by creating a phantasy about the original and unisexual being where desires, sexualities, phantasies and identities haven t been diverged. This can be fantasized in terms of art which forms a double for the melancholic subject who is in this limited and imaginary way able to forget for a while one s existential solitude.

Ruumiinkuvia! : Suomalainen performanssi- ja kehotaide 1980- ja1990-luvulla psykoanalyysin valossa

My PhD-thesis Body Images! Psychoanalytical Analysis of Finnish Performance and Body Art in the 1980s and 1990s considers Finnish performance and body art performed mainly by visual artists. In Part I, I chart the historical construction of performance art and its extension since the beginning of the 21st century. There are several wievs of the historical background of performance art. I introduce three different genealogies of performance art. One is Rose-Lee Goldberg s view. She connects performance art with the European avant-garde already at the beginning of the 20th century from futurists and dadaists to Russian avant-garde and the Bauhaus. I prefer to present performance art as contemporary art, which began to take shape in connection with visual arts in the 1950s and 1960s. The focus on the body is apparent in nearly all performance art. Nevertheless, throug the concept of body art I want to empasize the artist s body as the place of art. Body art (as part of performance art) functions as thematic and interpretive concept, which allows me to focus on performances where the questions of body image, narcissism, desire, language and pleasure are incorporated in particular intensive ways. In Part II, I explore the arrival of performance art in Finnish visual arts in the 1980s. I study the new generation s relation to earlier Finnish happenings (1960s) and performative actions in 1970 s. I briefly introduce performance groups of the 1980s art scene and consider their reception in media. The main focus is on the group Jack Helen Brut, in which I see many similarities to the so- called Theatre of Images. The goal of this part II is to provide historical context for the performance analysis that follows. In Part III, I develop the concept of body image which is my main theoretical term. The concept of body image is used according to Lacanian psychoanalytical theory, especially his considerations of mirror stages. My first mapping of body image, which I call imaginary body image, is based on Lacan s famous mirror stage article (1949). According to my reading, body image is narcistic and aggressive. The important concepts here are ego, imaginary, méconnaisance and alienation. In 1953 Lacan began to develop different version on mirror stage, in which he emphasized the primacy of symbolic dimension. It is not image, but language which constructs the foundations of body image. Central concepts in this chater are Other as language, ego-ideal, demand and desire. In the last chapter I connect the third version of the mirror stage to concepts of gaze, phantasy, real, jouissance and object a. In previous chapters I had considered body image in relation to ego. Now I explore it in relation to subject. In my reading the body image is fragile phenomen, which oscillates between yearning for coherence and phantasies of fragmented images. Part IV of the thesis begins with an introduction to the central concepts and debates in performace studies over the last few decades. Important concepts are presence, performativity and theatricality. The main substance of my thesis, however, is the performance analysis, which focuses on works by three Finnish artists and one Finnish group. The first analysis concerns the performance (1992) of Kimmo Schroderus. I discuss the relationship between narcissism and body art and the changes in demands projected on body images of men in recent decades in a Euro-American context. I also explore this performance in relation to the myth of Narcissus, which I reinterpret through Narcissus s aggression against his own body. The group Homo S is the main subject of the next analysis. I discuss the relationship between feminist art and performance art, especially in the United States in the 1960s and 1970s. Homo S is different from this early performance art because of its anarchism, humor and rejection of all ideals. Homo S characterizes its performance Body Body (1983) as liberating vulgar feminism . Sociality and performance of erotic relations between women are central in Body Body. Pia Lindman s performances are the subjects of my third analysis. I study three of her performances: Olen muoto (1993), 17 and in love (1994) and Arranged views (1995). I interpret these performances as efforts to disperse the imaginary and symbolic structures of the body image. She constructs the peculiar object a and phantasy space of her own. In the last analysis I move from questions of image and gaze to a study of language, sound and jouissance. I discuss at a general level the performance of orality and helplesness (Hilflosigkeit) in body art. The central elements in Pentti Otto Koskinen s performances are the ear, listening and receptive gestures and postions. Perseveraatio (1998) can be understood representing as submission to the super-ego s power, which compels one to enjoy. I examine particularly closely the performance Maissi on hyvää ei missään nimessä maissia (1995), which I interpret as the return of a baby s body image to the liminal site of choice: language or jouissance?

Approaching Sacred Pregnancy : The Cult of the Visitation and Narrative Altarpieces in Late Fifteenth-Century Florence

The study focuses on the Visitation as a narrative subject of altarpieces in late fifteenth-century Florence. Although the Visitation was a well-known story in both verbal and visual representations since the early medieval period, it became a popular subject of altarpieces only towards the end of the fifteenth century. In this study, the first part provides an overview of the complex religious and historical background to an emerging cult of the Visitation. Devotional practices focusing on the Visitation belong in a context of late medieval Marian devotion and in 1389 a new feast of the Visitation was introduced into the liturgical calendar of the Catholic Church. Because of the ongoing schism within the Catholic Church, the feast was not unanimously accepted across Western Europe until the later part of the fifteenth century. Contrary to a widely disseminated view, the feast of the Visitation cannot be associated with Franciscan spirituality, but was rather a clearly defined Dominican project that primarily emphasised the importance of peace and unity within the Christian Church. Simultaneously with the gradual acceptance of the new feast, visual representations of the Visitation began to appear at the centre of altarpieces. The Visitation exemplifies an increasing preference for narrative subjects within the genre of the altarpiece. The second part of the study presents an analysis of the concept of the narrative altarpiece and highlights the complexities involved in combining a narrative content with the traditional devotional function of the altarpiece. In detailed case studies some prominent art works produced in Florence between 1490 and 1503 are discussed within a framework of contextual analysis, narrative theory and iconography. Altarpieces by Domenico Ghirlandaio, Piero di Cosimo and Mariotto Albertinelli represent visual manifestations of a cult of the Visitation with roots in late medieval devotional practices. At the same time, the altarpieces highlight the multiple functions of altarpieces in a culture where art works responded to a variety of social and religious needs. Building on earlier studies, each case study presents new insights and evidence not considered in previous art historical research.

Vikuroivia vilkaisuja : Ruumis, sukupuoli, seksuaalisuus ja visuaalisen kulttuurin tutkimus

The PhD dissertation "Bucking Glances: On Body, Gender, Sexuality and Visual Culture Research" consists of theoretical introduction and five articles published between 2002-2005. The articles analyze the position of visual representations in the processes of knowledge production on acceptable genders, bodies, and sexualities in contemporary Wes¬tern societies. The research material is heterogeneous, consisting of representations of contemporary art, advertisements, and fashion images. The ideological starting point of the PhD dissertation is the politics of the gaze and the methods used to expose this are the concepts of oppositional gaze, close reading, and resisting reading. The study situates visual representations in dialogue with the concepts of the grotesque and androgyny, as well as with queer-theory and theories of the gaze. The research challenges normative meanings of visual representations and opens up space for more non-conventional readings attached to femininity and masculinity. The visual material is read as troubling the prevailing heteronormative gender system. The dissertation also indicates how visual culture research utilizing the approach of queer theory can be fruitful in opposing and re-visioning changes in the repressive gender system. The article "A Heroic Male and A Beautiful Woman. Teemu Mäki, Orlan and the Ambivalence of the Grotesque Body" problematizes the concept of heroic masculinity through the analysis of the Finnish artist Teemu Mäki's masochistic performance The Good Friday (1989). It also analyzes cosmetic surgery, undertaken by the French artist Orlan, as a cultural tool in constructing and visualizing the contemporary, com¬mercial ideals of female beauty. The article "Boys Will Be Girls Will Be Boys Will Be Girls. The Ambivalence of Androgyny in Calvin Klein' Advertisements" is a close reading of the Calvin Klein perfume advertisement One (1998) in reference to the concept of androgyny. The critical point of the article is that androgynous male bodies allow the extension of the categorical boundaries of masculinity and homosexuality, whereas representations of androgynous women feed into the prevailing stereotypes of femininity, namely the fear of fat. The article "See-through Closet: Female Androgyny in the 1990s Fashion Images, New Woman and Lesbian Chic" analyzes the late 1990s fashion advertisements through the concept of female androgyny. The article argues that the figures of the masculine female androgynes in the late 1990s fashion magazines do not problematize the dichotomous gender binary. The women do not pass as men but produce a variation of heterosexual desirability. At the same time, the representations open up space for lesbian gazing and desiring. The article "Why are there no lesbian advertisements?" addresses the issue of femme gaze and desire in relation to heterosexual fashion advertisements from the British edition of the mainstream fashion magazine Vogue. The article considers possibilities for resistant femme visibility, identification, and desire. The article "Woman, Food, Home. Pirjetta Brander's and Heidi Romo's Works as Bucking Representations of Femininity" analyses the production and queering of heteronormative femininity and family through the analysis of art works. The article discusses how the term queer has been translated into Finnish. The article also introduces a new translation for the term queer: the noun vikuuri, i.e. faulty form and the verb vikuroida, i.e. to buck. In Finnish, the term vikuuri is the vernacular or broken form of the term figure, i.e. figuuri. Vikuuri represents all forms situated outside the norm and the normative.

The One and The Many : In the works of Heraclitus, Parmenides and Lao Zi

This paper concentrates on Heraclitus, Parmenides and Lao Zi. The focus is on their ideas on change and whether the world is essentially One or if it is composed of many entities. In the first chapter I go over some general tendences in Greek and Chinese philosophy. The differences in the cultural background have an influence in the ways philosophy is made, but the paper aims to show that two questions can be brought up when comparing the philosophies of Heraclitus, Parmenides and Lao Zi. The questions are; is the world essentially One or Many? Is change real and if it is, what is the nature of it and how does it take place? For Heraclitus change is real, and as will be shown later in the chapter, quite essential for the sustainability of the world-order (kosmos). The key-concept in the case of Heraclitus is Logos. Heraclitus uses Logos in several senses, most well known relating to his element-theory. But another important feature of the Logos, the content of real wisdom, is to be able to regard everything as one. This does not mean that world is essentially one for Heraclitus in the ontological sense, but that we should see the underlying unity of multiple phenomena. Heraclitus regards this as hen panta: All from One, One from All. I characterize Heraclitus as epistemic monist and an ontological pluralist. It is plausible that the views of Heraclitus on change were the focus of Parmenides’ severe criticism. Parmenides held the view that the world is essentially one and that to see it as consisting of many entities was the error of mortals, i.e. the common man and his philosophical predecessors. For Parmenides what-is, can be approached by two routes; The Way of Truth (Aletheia) and The Way of Seeming (Doxa). Aletheia essentially sees the world as one, where even time is an illusion. In Doxa Parmenides is giving an explanation of the world seen as consisting of many entities and this is his contribution to the line of thought of his predecessors. It should be noted that a strong emphasis is given to the Aletheia, whereas the world-view given is in Doxa is only probable. I go on to describe Parmenides as ontological monist, who gives some plausibility to pluralistic views. In the work of Lao Zi world can be seen as One or as consisting of Many entities. In my interpretation, Lao Zi uses Dao in two different senses; Dao is the totality of things or the order in change. The wu-aspect (seeing-without-form) attends the world as one, whereas the you-aspect attends the world of many entities. In wu-aspect, Dao refers to the totality of things, when in you-aspect Dao is the order or law in change. There are two insights in Lao Zi regarding the relationship between wu- and- you-apects; in ch.1 it is stated that they are two separate aspects in seeing the world, the other chapters regarding that you comes from wu. This naturally brings in the question whether the One is the peak of seeing the world as many. In other words, is there a way from pluralism to monism. All these considerations make it probable that the work attributed to Lao Zi has been added new material or is a compilation of oral sayings. In the end of the paper I will go on to give some insights on how Logos and Dao can be compared in a relevant manner. I also compare Parmenides holistic monism to Lao Zi’s Dao as nameless totality (i.e. in its wu-aspect). I briefly touch the issues of Heidegger and the future of comparative philosophy.

Groteski suomalaisessa kirjallisuudessa : Neljä tapaustutkimusta

The grotesque in Finnish literature. Four case studies The topic of the dissertation is the grotesque in Finnish literature. The dissertation is twofold. Firstly, it focuses on the genre tradition of the grotesque, especially its other main branch, which has been named, following in Bakhtin s footsteps, subjective ( chamber ) grotesque, to be distinguished from carnivalistic ( public square ) grotesque. Secondly, the dissertation analyses and interprets four fictional literary works within the context of the grotesque genre, constructed on the basis of previous research and literature. These works are the novel Rakastunut rampa (1922) by Joel Lehtonen, the novel Prins Efflam (1953, transl. into Finnish as Kalastajakylän prinssi) by Sally Salminen, the short story Orjien kasvattaja (1965) by Juhani Peltonen, and the novel Veljeni Sebastian (1985) by Annika Idström. What connects these stirring novels, representing early or full modernism, is the supposition that they belong to the tradition of the subjective grotesque, not only due to occasional details, but also in a more comprehensive manner. The premises are that genre is a significant part of the work and that reading a novel in the context of the genre tradition adds something essential to the interpretation of individual texts and reveals meanings that might otherwise go unnoticed. The main characteristic of the grotesque is breaking the norm. This is accomplished through different means: degradation, distortion, inversion, combination, exaggeration and multiplication. The most significant strategy for breaking the norm is incongruence: the grotesque combines conflicting or mutually exclusive categories and elements on different levels. Simultaneously, the grotesque unravels categorisations and questions our way of perceiving the world. The grotesque not only poses a threat to one s identity, but can also pose a threat to the cognitive process. An analysis of the fictional works is presented as case studies of each chosen work as a whole. The analysis is based on the method of close reading, which draws on both classical and postclassical narratology, and the analysis and interpretation are expanded within the genre tradition of the grotesque. The grotesque is also analysed in terms of its relationship to the neighbouring categories and genre traditions, such as the tragic, the sublime, the horror story and the coming-of-age story. This dissertation shows how the grotesque is constructed repeatedly on deviations from the norm as well as on incongruence, also in the works analysed, and how it stratifies in these novels on and between different levels, such as the story, text, narration, composition and the world of the novels. In all the works analysed, the grotesque reduces and subverts. Again and again it reveals different sides of humanity stripped of idealisation and glorification. The dissertation reveals that Finnish literature is not a solitary island, even regarding the grotesque, for it continues and offers variations of the common tradition of grotesque literature, and likewise draws on grotesque visual arts. This dissertation is the first monograph in Finnish literature research focusing on the subjective grotesque.

Visual completion in an illusory figure

The visual systems of humans and animals represent physical reality in a modified way, depending on the specific demands that the species in question has for survival. The ability to perceive visual illusions is found in independently evolved visual systems, from honeybees to humans. In humans, the ability emerges early, at the age of four months. Thus the perception of illusion is likely to reflect visual processes of fundamental importance for object perception in natural vision. The experiments reported in this thesis employed various modifications of the Kanizsa triangle, a drawn configuration composed of three black disks with missing sectors on a white background. The sectors appear to form the tips of a triangle. The visual system completes the physically empty area between the disks, generally called inducers, with giving the perception of an illusory triangle. The illusory triangle consists of an illusory surface bounded by illusory contours; the triangle appears brighter than and to lie above the background. If the sectors are coloured, the colour fills the illusory area, a phenomenon known as neon colour spreading . We investigated spatial limitations on the perception of Kanizsa-type illusions and how other stimuli and viewing parameters affected these limitations. We also studied complex configurations thick, bent, mobile and chromatic inducers - to determine whether illusions combining several attributes can be perceived. The results suggest that the visual system is highly effective in completing a percept. The perception of an illusory figure is spatially scale invariant when perceived at threshold. The processing time and the number of fixations modify the percept, making the perception of the illusion more probable in various viewing conditions. Furthermore, the fact that the illusion can be perceived when only one inducer is physically present at any given moment indicates the potential of single inducers. Apparently, modelling illusory figure perception will require a combination of low-level, local processes and higher-level integrative processes. Our studies with stimuli combining several attributes relevant to object perception demonstrate that the perception of an illusory figure is flexible and is maintained also when it contains colour and volume and when shown in movement. All in all, the results confirm the assumed importance of the visual processes related with the perception of illusory figures in everyday viewing. This is indicated by the variety of inducer modifications that can be made without destroying the percept. Furthermore, the illusion can acquire additional attributes from such modifications. Due to individual differences in the perception of illusory figures, universal values for absolute performance are not always meaningful, but stable trends and general relations do exist.

Visual search and eye movements: Studies of perceptual span

In visual search one tries to find the currently relevant item among other, irrelevant items. In the present study, visual search performance for complex objects (characters, faces, computer icons and words) was investigated, and the contribution of different stimulus properties, such as luminance contrast between characters and background, set size, stimulus size, colour contrast, spatial frequency, and stimulus layout were investigated. Subjects were required to search for a target object among distracter objects in two-dimensional stimulus arrays. The outcome measure was threshold search time, that is, the presentation duration of the stimulus array required by the subject to find the target with a certain probability. It reflects the time used for visual processing separated from the time used for decision making and manual reactions. The duration of stimulus presentation was controlled by an adaptive staircase method. The number and duration of eye fixations, saccade amplitude, and perceptual span, i.e., the number of items that can be processed during a single fixation, were measured. It was found that search performance was correlated with the number of fixations needed to find the target. Search time and the number of fixations increased with increasing stimulus set size. On the other hand, several complex objects could be processed during a single fixation, i.e., within the perceptual span. Search time and the number of fixations depended on object type as well as luminance contrast. The size of the perceptual span was smaller for more complex objects, and decreased with decreasing luminance contrast within object type, especially for very low contrasts. In addition, the size and shape of perceptual span explained the changes in search performance for different stimulus layouts in word search. Perceptual span was scale invariant for a 16-fold range of stimulus sizes, i.e., the number of items processed during a single fixation was independent of retinal stimulus size or viewing distance. It is suggested that saccadic visual search consists of both serial (eye movements) and parallel (processing within perceptual span) components, and that the size of the perceptual span may explain the effectiveness of saccadic search in different stimulus conditions. Further, low-level visual factors, such as the anatomical structure of the retina, peripheral stimulus visibility and resolution requirements for the identification of different object types are proposed to constrain the size of the perceptual span, and thus, limit visual search performance. Similar methods were used in a clinical study to characterise the visual search performance and eye movements of neurological patients with chronic solvent-induced encephalopathy (CSE). In addition, the data about the effects of different stimulus properties on visual search in normal subjects were presented as simple practical guidelines, so that the limits of human visual perception could be taken into account in the design of user interfaces.

Dynamics of contour, object and face processing in the human visual cortex

The neural basis of visual perception can be understood only when the sequence of cortical activity underlying successful recognition is known. The early steps in this processing chain, from retina to the primary visual cortex, are highly local, and the perception of more complex shapes requires integration of the local information. In Study I of this thesis, the progression from local to global visual analysis was assessed by recording cortical magnetoencephalographic (MEG) responses to arrays of elements that either did or did not form global contours. The results demonstrated two spatially and temporally distinct stages of processing: The first, emerging 70 ms after stimulus onset around the calcarine sulcus, was sensitive to local features only, whereas the second, starting at 130 ms across the occipital and posterior parietal cortices, reflected the global configuration. To explore the links between cortical activity and visual recognition, Studies II III presented subjects with recognition tasks of varying levels of difficulty. The occipito-temporal responses from 150 ms onwards were closely linked to recognition performance, in contrast to the 100-ms mid-occipital responses. The averaged responses increased gradually as a function of recognition performance, and further analysis (Study III) showed the single response strengths to be graded as well. Study IV addressed the attention dependence of the different processing stages: Occipito-temporal responses peaking around 150 ms depended on the content of the visual field (faces vs. houses), whereas the later and more sustained activity was strongly modulated by the observers attention. Hemodynamic responses paralleled the pattern of the more sustained electrophysiological responses. Study V assessed the temporal processing capacity of the human object recognition system. Above sufficient luminance, contrast and size of the object, the processing speed was not limited by such low-level factors. Taken together, these studies demonstrate several distinct stages in the cortical activation sequence underlying the object recognition chain, reflecting the level of feature integration, difficulty of recognition, and direction of attention.

Temporal acuity in developmental dyslexia across the life span : Tactile, auditory, visual, and crossmodal estimations

Taustaa Kehityksellinen dysleksia (lukivaikeus) on erityinen lukemaan oppimisen vaikeus, johon liittyy usein myös vaikeuksia kirjoittamaan oppimisessa. Lukivaikeuden oletetaan useissa tapauksissa johtuvan vaikeudesta käsitellä kielen äännerakenteita (fonologinen prosessointi). Tämä poikkeavuus voi olla joko lukivaikeuden perimmäinen syy tai vaihtoehtoisesti ongelmat äänteiden käsittelyssä voivat heijastaa jotain vielä perustavamman tason vaikeutta. Eräs tällainen ehdotettu perustavan tasoin syy on poikkeavuus aistien toiminnoissa, erityisesti aistien aikatarkkuudessa. Aikatarkkuudella tarkoitetaan kykyä ja rajoja siinä, kuinka nopeasti esitettyä aistitiedon virtaa henkilö kykenee vastaanottamaan ja käsittelemään. Monet arjen toiminnot lukemisen rinnalla edellyttävät aistien erittäin tarkkaa ajallista erottelukykyä (esimerkiksi kuulo puheen ymmärtämisessä, tunto pintamateriaalin tunnistamisessa). Aikatarkkuusvaikeuksien esiintyvyyttä lukivaikeudessa on tutkittu aiemminkin, mutta yksimielisyyteen ei ole päästy siitä, onko kaikilla lukivaikeuksisilla näitä ongelmia tai mihin aisteihin vaikeudet mahdollisesti rajoittuvat. Myöskään ei tiedetä, havaitaanko aikatarkkuuden ongelmia kaiken ikäisillä lukivaikeuksisilla vai vaihteleeko mahdollinen ongelmien kuva iän mukana. Lisäksi on epäselvää, kuinka aikatarkkuuden ongelmat itseasiassa ovat yhteydessä kielen käsittelyn ja varsinaisen lukemisen vaikeuksiin. Tutkimussarjan aihe Tässä tutkimussarjassa aikatarkkuutta tutkittiin kolmessa yksittäisessä aistissa, joita olivat tunto, näkö ja kuulo, sekä kolmessa aistien välisessä yhdistelmässä, joita olivat audiotaktiilinen (kuulo-tunto), visuotaktiilinen (näkö-tunto) ja audiovisuaalinen (näkö-kuulo). Aikatarkkuutta arvioitiin kahdella eri menetelmällä, jotta saataisiin lisää tietoa siitä, missä tietyssä aikatarkkuuden osa-alueessa lukivaikeuksisilla mahdollisesti on vaikeuksia. Ensimmäisessä tehtävässä tutkittavan tuli arvioida, ovatko esitetyt ei-kielelliset ärsykkeet samanaikaisia vai eriaikaisia. Toisessa tehtävässä koehenkilön tuli arvioida esitettyjen ei-kielellisten ärsykkeiden esitysjärjestys. Molemmissa tehtävissä määriteltiin millisekuntitasolla (sekunnin tuhannesosa) se esitysnopeus, jolla koehenkilö kykeni arvioimaan ärsykkeiden ajalliset suhteet oikein. Englanninkielinen demonstraatio aikatarkkuustehtävistä löytyy internetistä (http://www.helsinki.fi/hum/ylpsy/neuropsy). Itse aikatarkkuustehtävien lisäksi tutkimussarjassa arvioitiin tutkimushenkilöiden päättelykykyä, kielellisiä toimintoja ja lukemista. Tutkimushenkilöt Tutkimuksiin osallistui 53 lukivaikeuksista ja 66 sujuvaa lukijaa, jotka oli jaettu kolmeen pääikäryhmään: lapset (8-12 vuotta), nuoret aikuiset (20-36 vuotta) ja ikääntyneemmät aikuiset (20-59 vuotta). Ikääntyneempien aikuisten ryhmä oli edelleen jaettu ikävuosikymmenluokkiin, mikä mahdollisti sen tutkimisen, vaikuttaako lisääntyvä aikuisikä lukivaikeuksisten aikatarkkuuteen (20-29, 30-39, 40-49 ja 50-59 -vuotiaat). Tutkimussarjan tulokset Aikatarkkuuden ongelmat lukivaikeuksisilla olivat yleistyneitä yli iän, aistien ja tehtävien Lukivaikeuksiset kaikissa pääikäryhmissä (lapset, nuoret aikuiset, ikääntyneemmän aikuiset) tarvitsivat samanikäisiä sujuvia lukijoita hitaamman esitystahdin, jotta he kykenivät arvioimaan ei-kielellisten ärsykkeiden ajallisen esitystavan oikein. Tämä aikatarkkuuden ongelma havaittiin lukivaikeuksisilla kaikissa aisteissa (tunto, kuulo, näkö) ja niiden yhdistelmissä (audiotaktiilinen, visuotaktiilinen, audiovisuaalinen). Lukivaikeuksisten aikatarkkuusongelmat ilmenivät edelleen molemmissa tehtävätyypeissä (samanaikaisuuden ja järjestyksen arvioinnissa). Aikatarkkuus ja sen ongelmat olivat yhteydessä äänteiden käsittelyyn Aikatarkkuus oli yhteydessä äänteiden käsittelykykyyn (fonologiseen prosessointiin), niin lapsilla kuin aikuisillakin, kaikissa aisteissa, niiden yhdistelmissä ja tehtävätyypeissä. Yhteys ei-kielellisen aikatarkkuuden ja kielellisten toimintojen välillä oli kuitenkin selkeämpi lukivaikeuksisilla kuin sujuvilla lukijoilla. Tämä tarkoittaa, että etenkin lukivaikeuksisilla ryhmätason huono aikatarkkuus oli yhteydessä huonoon äänteiden käsittelyyn (fonologiseen prosessointiin) ja päinvastoin. Suoraa yhteyttä lukemisen ja aikatarkkuuden välillä ei kuitenkaan havaittu. Lisääntyvä aikuisikä heikensi lukivaikeuksisten aikatarkkuutta suhteettoman paljon Tiedonkäsittelyn nopeuden on toistuvasti osoitettu hidastuvan normaalissa ikääntymisessä. Lisääntyvä aikuisikä (20-59 -vuotiailla) heikensikin sekä sujuvien että lukivaikeuksisten aikatarkkuutta. Toisin sanoen, mitä iäkkäämmästä aikuisesta oli kysymys, sitä hitaammin hänelle tuli esittää ärsykkeet, jotta hän kykeni arvioimaan niiden ajalliset suhteet oikein. Tämä ikään liittyvä tavanomainen hidastuminen oli kuitenkin yllättäen suhteettoman nopeaa lukivaikeuksisilla. Toisin sanoen, jo nuorilla lukivaikeuksisilla havaittu aikatarkkuuden vaikeus (ryhmäero verrattuna sujuviin lukijoihin) ei pysynyt saman suuruisena, vaan ryhmien ero kasvoi aikuisiän lisääntyessä. Tulosten merkitys Lukivaikeuden osoitettiin tässä tutkimussarjassa olevan yhteydessä yleistyneeseen vaikeuteen käsitellä ajassa nopeasti muuttuvaa ei-kielellistä aistitietoa (yli aistien ja niiden yhdistelmien, tehtävätyyppien, tutkittavien iän). Tämä osoittaa, että lukivaikeus ei ole ongelma, joka rajoittuu vain kielellisen materiaalin käsittelyn vaikeuksiin (äänteiden käsittely, lukeminen, kirjoittaminen). Nyt havaitut vaikeudet eivät myöskään rajoittuneet vain niihin aisteihin, jotka selkeimmin liittyvät lukemiseen (näkö) ja puhuttuun kieleen (kuulo); Ongelmia esiintyi myös muissa aisteissa (tunto). Lukivaikeuksisten lukijoiden ryhmätasolla havaittu aikatarkkuuden ongelma ei kuitenkaan heijastunut yksilötasolle; Jokainen lukivaikeuksinen ei ollut huono aikatarkkuustehtävissä. Näin ollen ei siis voida väittää, että kaikkien lukivaikeuksisten äänteiden käsittelyn tai lukemaan oppimisen vaikeudet voisivat selittyä aistien toimintojen poikkeavuudella. Aikatarkkuuden ongelmat eivät olleet yhteydessä varsinaiseen lukemiseen. Sekä lukivaikeuksisilla lapsilla että aikuisilla todettiin kuitenkin selkeä yhteys aikatarkkuuden ongelmien ja lukemaan oppimisen keskeisen ennakkoehdon, fonologisen prosessoinnin, välillä. Saattaa siis olla, että synnynnäinen aistien toimintojen poikkeavuus vaikuttaa yksilön suoriutumiseen jo ennen varsinaista lukemaan oppimista, kun ne taidot kehittyvät (fonologinen prosessointi), joille myöhempi lukemaan oppiminen perustuu. Ikäännyttäessä havaittu lukivaikeuksisten suhteettoman nopea aikatarkkuuden heikkeneminen osoittaa, että lukivaikeus ei voi olla ongelma, joka koskee vain lapsuusikää, tai vaikeus, joka johtuu vain kehityksen viivästymästä joka kurottaisiin iän myötä umpeen. Tulosten ymmärtämiseksi onkin muistettava kaksi seikkaa. Lukivaikeus on ensinnäkin yhdistetty synnynnäisiin, pieniin, poikkeavuuksiin aivojen rakenteissa ja toiminnoissa. Toisaalta tavanomaiseen ikääntymiseen liittyy se, että aivot kykenevät yhä huonommin korjaamaan ja kiertämään (kompensoimaan) pieniä vaurioita. Tämän perusteella tutkimussarjan tuloksista voidaan päätellä, että lukivaikeuksisten jo synnynnäisesti heikentyneet aivojen kompensointimahdollisuudet eivät ole yhtä tehokkaita puskuroimaan ikääntymisen tavanomaisia vaikutuksia kuin sujuvilla lukijoilla. Yllättävää kuitenkin on, että tämä korostunut heikkeneminen havaittiin jo suhteellisen nuorilla, työikäisillä, lukivaikeuksisilla, ennen 60 ikävuotta. Samanlaista ikäännyttäessä korostuvaa vaikeutta ei lukivaikeuksilla kuitenkaan havaittu päättelyssä, kielellisissä toiminnoissa tai itse lukemisessa. Vaikuttaakin siis siltä, että ne toiminnot, joita on harjaannutettu aktiivisesti, eivät heikkene kasvavan aikuisiän myötä yhtä suhteettomasti. Alkuperäiset artikkelit Laasonen M, Tomma-Halme J, Lahti-Nuuttila P, Service E, and Virsu V (2000) Rate of information segregation in developmentally dyslexic children, Brain and Language, 75(1), 66-81. Laasonen M, Service E, and Virsu V (2001) Temporal order and processing acuity of visual, auditory, and tactile perception in developmentally dyslexic young adults, Cognitive, Affective, and Behavioral Neuroscience, 1(4), 394-410. Laasonen M, Service E, and Virsu V (2002) Crossmodal temporal order and processing acuity in developmentally dyslexic young adults, Brain and Language, 80(3), 340-354. Laasonen M, Lahti-Nuuttila P, and Virsu V (2002) Developmentally impaired processing speed decreases more than normally with age, NeuroReport, 13(9), 1111-1113.

Auditory - Visual Matching in Learning Disabilities : Intervention Studies from Finland and Sweden

The present thesis discusses relevant issues in education: 1) learning disabilities including the role of comorbidity in LDs, and 2) the use of research-based interventions. This thesis consists of a series of four studies (three articles), which deepens the knowledge of the field of special education. Intervention studies (N=242) aimed to examine whether training using a nonverbal auditory-visual matching computer program had a remedial effect in different learning disabilities, such as developmental dyslexia, Attention Deficit Disorder (ADD) and Specific Language Impairment (SLI). These studies were conducted in both Finland and Sweden. The intervention’s non-verbal character made an international perspective possible. The results of the intervention studies confirmed, that the auditory-visual matching computer program, called Audilex had positive intervention effects. In Study I of children with developmental dyslexia there were also improvements in reading skills, specifically in reading nonsense words and reading speed. These improvements in tasks, which are thought to rely on phonological processing, suggest that such reading difficulties in dyslexia may stem in part from more basic perceptual difficulties, including those required to manage the visual and auditory components of the decoding task. In Study II the intervention had a positive effect on children with dyslexia; older students with dyslexia and surprisingly, students with ADD also benefited from this intervention. In conclusion, the role of comorbidity was apparent. An intervention effect was evident also in students’ school behavior. Study III showed that children with SLI experience difficulties very similar to those of children with dyslexia in auditory-visual matching. Children with language-based learning disabilities, such as dyslexia and SLI benefited from the auditory-visual matching intervention. Also comorbidity was evident among these children; in addition to formal diagnoses, comorbidity was explored with an assessment inventory, which was developed for this thesis. Interestingly, an overview of the data of this thesis shows positive intervention effects in all studies despite learning disability, language, gender or age. These findings have been described by a concept inter-modal transpose. Self-evidently these issues need further studies. In learning disabilities the aim in the future will also be to identify individuals at risk rather than by deficit; this aim can be achieved by using research-based interventions, intensified support in general education and inclusive special education. Keywords: learning disabilities, developmental dyslexia, attention deficit disorder, specific language impairment, language-based learning disabilities, comorbidity, auditory-visual matching, research-based interventions, inter-modal transpose