Effects of visuospatial tasks on desensitization to emotive memories

Objectives. Intrusive memories of extreme trauma can disrupt a stepwise approach to imaginal exposure. Concurrent tasks that load the visuospatial sketchpad (VSSP) of working memory reduce the vividness of recalled images. This study tested whether relief of distress from competing VSSP tasks during imaginal exposure is at the cost of impaired desensitization. Design. This study examined repeated exposure to emotive memories using 18 unselected undergraduates and a within-subjects design with three exposure conditions (Eye Movement, Visual Noise, Exposure Alone) in random, counterbalanced order. Method. At baseline, participants recalled positive and negative experiences, and rated the vividness and emotiveness of each image. A different positive and negative recollection was then used for each condition. Vividness and emotiveness were rated after each of eight exposure trials. At a post-exposure session 1 week later, participants rated each image without any concurrent task. Results. Consistent with previous research, vividness and distress during imaging were lower during Eye Movements than in Exposure Alone, with passive visual interference giving intermediate results. A reduction in emotional responses from Baseline to Post was of similar size for the three conditions. Conclusion. Visuospatial tasks may offer a temporary response aid for imaginal exposure without affecting desensitization.

Brain activity during the encoding, retention, and retrieval of stimulus representations

Studies of delayed nonmatching-to-sample (DNMS) performance following lesions of the monkey cortex have revealed a critical circuit of brain regions involved in forming memories and retaining and retrieving stimulus representations. Using event-related functional magnetic resonance imaging (fMRI), we measured brain activity in 10 healthy human participants during performance of a trial-unique visual DNMS task using novel barcode stimuli. The event-related design enabled the identification of activity during the different phases of the task (encoding, retention, and retrieval). Several brain regions identified by monkey studies as being important for successful DNMS performance showed selective activity during the different phases, including the mediodorsal thalamic nucleus (encoding), ventrolateral prefrontal cortex (retention), and perirhinal cortex (retrieval). Regions showing sustained activity within trials included the ventromedial and dorsal prefrontal cortices and occipital cortex. The present study shows the utility of investigating performance on tasks derived from animal models to assist in the identification of brain regions involved in human recognition memory.

Human cortical processing of colour and pattern

The present study investigates human visual processing of simple two-colour patterns using a delayed match to sample paradigm with positron emission tomography (PET). This study is unique in that we specifically designed the visual stimuli to be the same for both pattern and colour recognition with all patterns being abstract shapes not easily verbally coded composed of two-colour combinations. We did this to explore those brain regions required for both colour and pattern processing and to separate those areas of activation required for one or the other. We found that both tasks activated similar occipital regions, the major difference being more extensive activation in pattern recognition. A right-sided network that involved the inferior parietal lobule, the head of the caudate nucleus, and the pulvinar nucleus of the thalamus was common to both paradigms. Pattern recognition also activated the left temporal pole and right lateral orbital gyrus, whereas colour recognition activated the left fusiform gyrus and several right frontal regions. (C) 2001 Wiley-Liss, Inc.

A cognitive complexity metric applied to cognitive development

Two experiments tested predictions from a theory in which processing load depends on relational complexity (RC), the number of variables related in a single decision. Tasks from six domains (transitivity, hierarchical classification, class inclusion, cardinality, relative-clause sentence comprehension, and hypothesis testing) were administered to children aged 3-8 years. Complexity analyses indicated that the domains entailed ternary relations (three variables). Simpler binary-relation (two variables) items were included for each domain. Thus RC was manipulated with other factors tightly controlled. Results indicated that (i) ternary-relation items were more difficult than comparable binary-relation items, (ii) the RC manipulation was sensitive to age-related changes, (iii) ternary relations were processed at a median age of 5 years, (iv) cross-task correlations were positive, with all tasks loading on a single factor (RC), (v) RC factor scores accounted for 80% (88%) of age-related variance in fluid intelligence (compositionality of sets), (vi) binary- and ternary-relation items formed separate complexity classes, and (vii) the RC approach to defining cognitive complexity is applicable to different content domains. (C) 2002 Elsevier Science (USA). All rights reserved.

Ocular scanning and perceptual size distortion in hemispatial neglect: effects of prism adaptation and sequential stimulus presentation

When asked to compare two lateralized shapes for horizontal size, neglect patients often indicate the left stimulus to be smaller. Gainotti and Tiacci (1971) hypothesized that this phenomenon might be related to a rightward bias in the patients' gaze. This study aimed to assess the relation between this size underestimation and oculomotor asymmetries. Eye movements were recorded while three neglect patients judged the horizontal extent of two rectangles. Two experimental manipulations were performed to increase the likelihood of symmetrical scanning of the stimulus display. The first manipulation entailed a sequential, rather than simultaneous presentation of the two rectangles. The second required adaptation to rightward displacing prisms, which is known to reduce many manifestations of neglect. All patients consistently underestimated the left rectangle, but the pattern of verbal responses and eye movements suggested different underlying causes. These include a distortion of space perception without ocular asymmetry, a failure to view the full leftward extent of the left stimulus, and a high-level response bias. Sequential presentation of the rectangles and prism adaptation reduced ocular asymmetries without affecting size underestimation. Overall, the results suggest that leftward size underestimation in neglect can arise for a number of different reasons. Incomplete leftward scanning may perhaps be sufficient to induce perceptual size distortion, but it is not a necessary prerequisite.

Cortex, cognition and the cell: New insights into the pyramidal neuron and prefrontal function

Arguably the most complex conical functions are seated in human cognition, the how and why of which have been debated for centuries by theologians, philosophers and scientists alike. In his best-selling book, An Astonishing Hypothesis: A Scientific Search for the Soul, Francis Crick refined the view that these qualities are determined solely by cortical cells and circuitry. Put simply, cognition is nothing more, or less, than a biological function. Accepting this to be the case, it should be possible to identify the mechanisms that subserve cognitive processing. Since the pioneering studies of Lorent de No and Hebb, and the more recent studies of Fuster, Miller and Goldman-Rakic, to mention but a few, much attention has been focused on the role of persistent neural activity in cognitive processes. Application of modern technologies and modelling techniques has led to new hypotheses about the mechanisms of persistent activity. Here I focus on how regional variations in the pyramidal cell phenotype may determine the complexity of cortical circuitry and, in turn, influence neural activity. Data obtained from thousands of individually injected pyramidal cells in sensory, motor, association and executive cortex reveal marked differences in the numbers of putative excitatory inputs received by these cells. Pyramidal cells in prefrontal cortex have, on average, up to 23 times more dendritic spines than those in the primary visual area. I propose that without these specializations in the structure of pyramidal cells, and the circuits they form, human cognitive processing would not have evolved to its present state. I also present data from both New World and Old World monkeys that show varying degrees of complexity in the pyramidal cell phenotype in their prefrontal cortices, suggesting that cortical circuitry and, thus, cognitive styles are evolving independently in different species.

Hierarchical Reinforcement Learning in Behavior and the Brain

Dissertation presented to obtain the Ph.D degree in Biology, Neuroscience

Computational modeling of prefrontal cortex circuits

Dissertation presented to obtain the Ph.D degree in Biology

Product quality judgments in a two-sequence cue environment

Previous research demonstrated that the sequence of informational cues and the level of distraction have an impact on the judgment of a product’s quality. This study investigates the influence of the force behind the processing of these cues, working memory (WM). The results indicate that without distraction, consumers with low and high WM capacity (WMC) equally base their product evaluation on the first sequential cue. In the presence of a distractor, however, low WM individuals are no longer able to recall the initial cue, and thus derive their product judgment from the final cue. Moreover, evidence of intercultural differences in the perception of product related cues, and their aptitude for signaling a favorable product quality is provided.

Cognitive rehabilitation in a visual variant of Alzheimer's disease

Alzheimer's disease (AD) is commonly associated with marked memory deficits; however, nonamnestic variants have been consistently described as well. Posterior cortical atrophy (PCA) is a progressive degenerative condition in which posterior regions of the brain are predominantly affected, therefore resulting in a pattern of distinctive and marked visuospatial symptoms, such as apraxia, alexia, and spatial neglect. Despite the growing number of studies on cognitive and neural bases of the visual variant of AD, intervention studies remain relatively sparse. Current pharmacological treatments offer modest efficacy. Also, there is a scarcity of complementary nonpharmacological interventions with only two previous studies of PCA. Here we describe a highly educated 57-year-old patient diagnosed with a visual variant of AD who participated in a cognitive intervention program (comprising reality orientation, cognitive stimulation, and cognitive training exercises). Neuropsychological assessment was performed across moments (baseline, postintervention, follow-up) and consisted mainly of verbal and visual memory. Baseline neuropsychological assessment showed deficits in perceptive and visual-constructive abilities, learning and memory, and temporal orientation. After neuropsychological rehabilitation, we observed small improvements in the patient's cognitive functioning, namely in verbal memory, attention, and psychomotor abilities. This study shows evidence of small beneficial effects of cognitive intervention in PCA and is the first report of this approach with a highly educated patient in a moderate stage of the disease. Controlled studies are needed to assess the potential efficacy of cognition-focused approaches in these patients, and, if relevant, to grant their availability as a complementary therapy to pharmacological treatment and visual aids.

Concepts and objects of awareness in Alzheimer’s disease: an updated systematic review

ABSTRACT Objectives To compare and discuss the objects of awareness in Alzheimer’s disease (AD): awareness of cognitive deficits, of functional activities, of social-emotional functioning and behavioral impairment. Methods A search in the PsycINFo, Pilots, PubMed/Medline and ISI electronic databases according to Prisma methodology was performed. We included studies about awareness in people with AD published between 2010 and 2015, with the combination of keywords: “Alzheimer AND awareness of deficits”, “Alzheimer AND anosognosia”, “Alzheimer AND insight”, “dementia AND awareness of deficits”, “dementia AND anosognosia”, “dementia AND insight”. The articles were categorized according to the specific object of awareness. Results Seven hundred and ten records were identified and, after application of the exclusion criteria, 191 studies were retrieved for potential use. After excluding the duplicates, 46 studies were included. Most studies assessed the cognitive domain of awareness, followed by the functional, social-emotional, and behavioral impairment domains. Memory deficits were not sufficient to explain impaired awareness in AD. Longitudinal studies did not find discrepancies between patients and caregivers’ reports, indicating that awareness is not related to cognition. Conflicting findings were observed, including the relation between awareness, mood, severity of disease, and personal characteristics. Conclusions The studies show lack of conceptual consensus and significant methodological differences. The inclusion of samples without differentiation of dementia etiology is associated to symptomatic differences, which affect awareness domains. Awareness in AD is a complex and multidimensional construct. Different objects elicit different levels of awareness.

Can genetic algorithms explain experimental anomalies? An application to common property resources

It is common to find in experimental data persistent oscillations in the aggregate outcomes and high levels of heterogeneity in individual behavior. Furthermore, it is not unusual to find significant deviations from aggregate Nash equilibrium predictions. In this paper, we employ an evolutionary model with boundedly rational agents to explain these findings. We use data from common property resource experiments (Casari and Plott, 2003). Instead of positing individual-specific utility functions, we model decision makers as selfish and identical. Agent interaction is simulated using an individual learning genetic algorithm, where agents have constraints in their working memory, a limited ability to maximize, and experiment with new strategies. We show that the model replicates most of the patterns that can be found in common property resource experiments.

Investigació integrada amb EPs i RMf de la interacció entre la memòria de treball i la distracció

Estudi elaborat a partir d’una estada a la University of Wales, Bangor, Regne Unit entre setembre i desembre del 2006. Els sons distractors augmenten el temps de reacció i el nombre de respostes incorrectes en una tasca de classificació visual, demostrant que hi ha distracció conductual durant la realització de la tasca visual. L’enregistrament concomitant de potencials evocats durant la distracció mostra un patró neuroelèctric característic, el potencial de distracció, que es caracteritza per una ona trifàsica. Darrerament, s’ha demostrat que factors “des de dalt” associats al muntatge experimental tindrien una gran influència en els efectes que els estímuls distractors tindrien en la tasca. Estudis recents mostrarien que aquesta resposta d’atenció exògena es pot modular per la càrrega en memòria de treball, reduint-ne la distracció amb la càrrega, fet que contradiu altres dades que mostraven l’efecte oposat. L’objectiu d’aquest estudi ha estat investigar en quines condicions la càrrega en memòria de treball pot exercir un efecte modulador en les respostes conductuals i cerebrals als sons novedosos distractors, i establir la dinàmica espacio-temporal d’aquesta modulació.

The contribution of aging to the understanding of the dimensionality of executive functions.

It has been reported in the literature that executive functions may be fractioned into updating, shifting, and inhibition. The present study aimed to explore whether these executive sub-components can be identified in a more age-heterogeneous sample and see if they are prone to an age-related decline. We tested the performances of 81 individuals aged from 18 to 88 years old in each executive sub-component, working memory, fluid intelligence and processing speed. Correlation analysis revealed only a slight positive relationship between the two updating measures. A linear decrement with age was observed only for two complex executive tests. Tasks indexing working memory, processing speed and fluid intelligence showed a stronger linear decline with age than executive tasks. In conclusion, our results did not replicate the executive structure known from the literature, and revealed that decrement in executive function is not an unavoidable concomitant of aging but rather concerns specific executive tasks.

Poor reward sensitivity and apathy after stroke: implication of basal ganglia.

OBJECTIVE: To examine the relationship between reward sensitivity and self-reported apathy in stroke patients and to investigate the neuroanatomical correlates of both reward sensitivity and apathy. METHODS: In this prospective study, 55 chronic stroke patients were administered a questionnaire to assess apathy and a laboratory task to examine reward sensitivity by measuring motivationally driven behavior ("reinforcement-related speeding"). Fifteen participants without brain damage served as controls for the laboratory task. Negative mood, working memory, and global cognitive functioning were also measured to determine whether reward insensitivity and apathy were secondary to cognitive impairments or negative mood. Voxel-based lesion-symptom mapping was used to explore the neuroanatomical substrates of reward sensitivity and apathy. RESULTS: Participants showed reinforcement-related speeding in the highly reinforced condition of the laboratory task. However, this effect was significant for the controls only. For patients, poorer reward sensitivity was associated with greater self-reported apathy (p < 0.05) beyond negative mood and after lesion size was controlled for. Neither apathy nor reward sensitivity was related to working memory or global cognitive functioning. Voxel-based lesion-symptom mapping showed that damage to the ventral putamen and globus pallidus, dorsal thalamus, and left insula and prefrontal cortex was associated with poorer reward sensitivity. The putamen and thalamus were also involved in self-reported apathy. CONCLUSIONS: Poor reward sensitivity in stroke patients with damage to the ventral basal ganglia, dorsal thalamus, insula, or prefrontal cortex constitutes a core feature of apathy. These results provide valuable insight into the neural mechanisms and brain substrate underlying apathy.