Receding and disparity cues aid relaxation of accommodation

Purpose. Accommodation can mask hyperopia and reduce the accuracy of non-cycloplegic refraction. It is, therefore, important to minimize accommodation to obtain a measure of hyperopia as accurate as possible. To characterize the parameters required to measure the maximally hyperopic error using photorefraction, we used different target types and distances to determine which target was most likely to maximally relax accommodation and thus more accurately detect hyperopia in an individual. Methods. A PlusoptiX SO4 infra-red photorefractor was mounted in a remote haploscope which presented the targets. All participants were tested with targets at four fixation distances between 0.3 and 2 m containing all combinations of blur, disparity, and proximity/looming cues. Thirty-eight infants (6 to 44 weeks) were studied longitudinally, and 104 children [4 to 15 years (mean 6.4)] and 85 adults, with a range of refractive errors and binocular vision status, were tested once. Cycloplegic refraction data were available for a sub-set of 59 participants spread across the age range. Results. The maximally hyperopic refraction (MHR) found at any time in the session was most frequently found when fixating the most distant targets and those containing disparity and dynamic proximity/looming cues. Presence or absence of blur was less significant, and targets in which only single cues to depth were present were also less likely to produce MHR. MHR correlated closely with cycloplegic refraction (r = 0.93, mean difference 0.07 D, p = n.s., 95% confidence interval +/-<0.25 D) after correction by a calibration factor. Conclusions. Maximum relaxation of accommodation occurred for binocular targets receding into the distance. Proximal and disparity cues aid relaxation of accommodation to a greater extent than blur, and thus non-cycloplegic refraction targets should incorporate these cues. This is especially important in screening contexts with a brief opportunity to test for significant hyperopia. MHR in our laboratory was found to be a reliable estimation of cycloplegic refraction. (Optom Vis Sci 2009;86:1276-1286)

A novel experimental method for measuring vergence and accommodation responses to the main near visual cues in typical and atypical groups

Binocular disparity, blur, and proximal cues drive convergence and accommodation. Disparity is considered to be the main vergence cue and blur the main accommodation cue. We have developed a remote haploscopic photorefractor to measure simultaneous vergence and accommodation objectively in a wide range of participants of all ages while fixating targets at between 0.3 and 2 m. By separating the three main near cues, we can explore their relative weighting in three-, two-, one-, and zero-cue conditions. Disparity can be manipulated by remote occlusion; blur cues manipulated by using either a Gabor patch or a detailed picture target; looming cues by either scaling or not scaling target size with distance. In normal orthophoric, emmetropic, symptom-free, naive visually mature participants, disparity was by far the most significant cue to both vergence and accommodation. Accommodation responses dropped dramatically if disparity was not available. Blur only had a clinically significant effect when disparity was absent. Proximity had very little effect. There was considerable interparticipant variation. We predict that relative weighting of near cue use is likely to vary between clinical groups and present some individual cases as examples. We are using this naturalistic tool to research strabismus, vergence and accommodation development, and emmetropization.

Humans ignore motion and stereo cues in favor of a fictional stable world

As we move through the world, our eyes acquire a sequence of images. The information from this sequence is sufficient to determine the structure of a three-dimensional scene, up to a scale factor determined by the distance that the eyes have moved [1, 2]. Previous evidence shows that the human visual system accounts for the distance the observer has walked [3,4] and the separation of the eyes [5-8] when judging the scale, shape, and distance of objects. However, in an immersive virtual-reality environment, observers failed to notice when a scene expanded or contracted, despite having consistent information about scale from both distance walked and binocular vision. This failure led to large errors in judging the size of objects. The pattern of errors cannot be explained by assuming a visual reconstruction of the scene with an incorrect estimate of interocular separation or distance walked. Instead, it is consistent with a Bayesian model of cue integration in which the efficacy of motion and disparity cues is greater at near viewing distances. Our results imply that observers are more willing to adjust their estimate of interocular separation or distance walked than to accept that the scene has changed in size.

Learning associations between places and visual cues without learning to navigate: neither fornix nor entorhinal cortex is required

Rats with fornix transection, or with cytotoxic retrohippocampal lesions that removed entorhinal cortex plus ventral subiculum, performed a task that permits incidental learning about either allocentric (Allo) or egocentric (Ego) spatial cues without the need to navigate by them. Rats learned eight visual discriminations among computer-displayed scenes in a Y-maze, using the constant-negative paradigm. Every discrimination problem included two familiar scenes (constants) and many less familiar scenes (variables). On each trial, the rats chose between a constant and a variable scene, with the choice of the variable rewarded. In six problems, the two constant scenes had correlated spatial properties, either Alto (each constant appeared always in the same maze arm) or Ego (each constant always appeared in a fixed direction from the start arm) or both (Allo + Ego). In two No-Cue (NC) problems, the two constants appeared in randomly determined arms and directions. Intact rats learn problems with an added Allo or Ego cue faster than NC problems; this facilitation provides indirect evidence that they learn the associations between scenes and spatial cues, even though that is not required for problem solution. Fornix and retrohippocampal-lesioned groups learned NC problems at a similar rate to sham-operated controls and showed as much facilitation of learning by added spatial cues as did the controls; therefore, both lesion groups must have encoded the spatial cues and have incidentally learned their associations with particular constant scenes. Similar facilitation was seen in subgroups that had short or long prior experience with the apparatus and task. Therefore, neither major hippocampal input-output system is crucial for learning about allocentric or egocentric cues in this paradigm, which does not require rats to control their choices or navigation directly by spatial cues.

Reverberant auditory environments: the effects of multiple echoes on distraction by 'irrelevant' speech

Two experiments examine the effect on an immediate recall test of simulating a reverberant auditory environment in which auditory distracters in the form of speech are played to the participants (the 'irrelevant sound effect'). An echo-intensive environment simulated by the addition of reverberation to the speech reduced the extent of 'changes in state' in the irrelevant speech stream by smoothing the profile of the waveform. In both experiments, the reverberant auditory environment produced significantly smaller irrelevant sound distraction effects than an echo-free environment. Results are interpreted in terms of changing-state hypothesis, which states that acoustic content of irrelevant sound, rather than phonology or semantics, determines the extent of the irrelevant sound effect (ISE). Copyright (C) 2007 John Wiley & Sons, Ltd.

Auditory distraction from low-intensity noise: a review of the consequences for learning and workplace environments

The 'irrelevant sound effect' in short-term memory is commonly believed to entail a number of direct consequences for cognitive performance in the office and other workplaces (e.g. S. P. Banbury, S. Tremblay, W. J. Macken, & D. M. Jones, 2001). It may also help to identify what types of sound are most suitable as auditory warning signals. However, the conclusions drawn are based primarily upon evidence from a single task (serial recall) and a single population (young adults). This evidence is reconsidered from the standpoint of different worker populations confronted with common workplace tasks and auditory environments. Recommendations are put forward for factors to be considered when assessing the impact of auditory distraction in the workplace. Copyright (c) 2005 John Wiley & Sons, Ltd.

Perceptual cues for orientation in a two finger haptic grasp task

Single point interaction haptic devices do not provide the natural grasp and manipulations found in the real world, as afforded by multi-fingered haptics. The present study investigates a two-fingered grasp manipulation involving rotation with and without force feedback. There were three visual cue conditions: monocular, binocular and projective lighting. Performance metrics of time and positional accuracy were assessed. The results indicate that adding haptics to an object manipulation task increases the positional accuracy but slightly increases the overall time taken.

Understanding of auditory discourse in older adults: the effects of syntax and working memory

Background: As people age, language-processing ability changes. While several factors modify discourse comprehension ability in older adults, syntactic complexity of auditory discourse has received scant attention. This is despite the widely researched domain of syntactic processing of single sentences in older adults. Aims: The aims of this study were to investigate the ability of healthy older adults to understand stories that differed in syntactic complexity, and its relation to working memory. Methods & Procedures: A total of 51 healthy adults (divided into three age groups) took part. They listened to brief stories (syntactically simple and syntactically complex) and had to respond to false/true comprehension probes following each story. Working memory capacity (digit span, forward and backward) was also measured. Outcomes & Results: Differences were found in the ability of healthy older adults to understand simple and complex discourse. The complex discourse in particular was more sensitive in discerning age-related language patterns. Only the complex discourse task correlated moderately with age. There was no correlation between age and simple discourse. As far as working memory is concerned, moderate correlations were found between working memory and complex discourse. Education did not correlate with discourse, neither simple, nor complex. Conclusions: Older adults may be less efficient in forming syntactically complex representations and this may be influenced by limitations in working memory.

Room-acoustic factors in attentional tracking

In a “busy” auditory environment listeners can selectively attend to one of several simultaneous messages by tracking one listener's voice characteristics. Here we ask how well other cues compete for attention with such characteristics, using variations in the spatial position of sound sources in a (virtual) seminar room. Listeners decided which of two simultaneous target words belonged in an attended “context” phrase when it was played with a simultaneous “distracter” context that had a different wording. Talker difference was in competition with a position difference, so that the target‐word chosen indicates which cue‐type the listener was tracking. The main findings are that room‐acoustic factors provide some tracking cues, whose salience increases with distance separation. This increase is more prominent in diotic conditions, indicating that these cues are largely monaural. The room‐acoustic factors might therefore be the spectral‐ and temporal‐envelope effects of reverberation on the timbre of speech. By contrast, the salience of cues associated with differences in sounds' bearings tends to decrease with distance, and these cues are more effective in dichotic conditions. In other conditions, where a distance and a bearing difference cooperate, they can completely override a talker difference at various distances.

Auditory hallucinations and Posttraumatic Stress Disorder within schizophrenia and substance abuse

There is a high prevalence of traumatic events within individuals diagnosed with schizophrenia, and of auditory hallucinations within individuals diagnosed with posttraumatic stress disorder (PTSD). However, the relationship between the symptoms associated with these disorders remains poorly understood. We conducted a multidimensional assessment of auditory hallucinations within a sample diagnosed with schizophrenia and substance abuse, both with and without co-morbid PTSD. Results suggest a rate of co-morbid PTSD similar to those reported within other studies. Patients who suffered co-morbid PTSD reported more distressing auditory hallucinations. However, the hallucinations were not more frequent or of longer duration. The need for a multidimensional assessment is supported. Results are discussed within current theoretical accounts of traumatic psychosis.

A cognitive and psycholinguistic investigation of neologisms

Background: Jargon aphasia with neologisms (i.e., novel nonword utterances) is a challenging language disorder that lacks a definitive theoretical description as well as clear treatment recommendations (Marshall, 2006). Aim: The aims of this two part investigation were to determine the source of neologisms in an individual with jargon aphasia (FF), to identify potential facilitatory semantic and/or phonological cuing effects in picture naming, and to determine whether the timing of the cues relative to the target picture mediated the cuing advantage. Methods and Procedures: FF’s underlying linguistic deficits were determined using several cognitive and linguistic tests. A series of computerized naming experiments using a modified version of the 175 item-Philadelphia Naming Test (Roach, Schwartz, Martin, Grewal, & Brecher, 1996) manipulated the cue type (semantic versus phonological) and relatedness (related versus unrelated). In a follow-up experiment, the relative timing of phonological cues was manipulated to test the effect of timing on the cuing advantage. The accuracy of naming responses and error patterns were analyzed. Outcome and Results: FF’s performance on the linguistic and cognitive test battery revealed a severe naming impairment with relatively spared word and nonword repetition, auditory comprehension of words and monitoring, and fairly well preserved semantic abilities. This performance profile was used to evaluate various explanations for neologisms including a loss of phonological codes, monitoring failure, and impairments in semantic system. The primary locus of his deficit appears to involve the connection between semantics to phonology, specifically, when word production involves accessing the phonological forms following semantic access. FF showed a significant cuing advantage only for phonological cues in picture naming, particularly when the cue preceded or coincided with the onset of the target picture. Conclusions: When integrated with previous findings, the results from this study suggest that the core deficit of this and at least some other jargon aphasics is in the connection from semantics to phonology. The facilitative advantage of phonological cues could potentially be exploited in future clinical and research studies to test the effectiveness of these cues for enhancing naming performance in individuals like FF.

The use of cues to convergence and accommodation in naive, uninstructed participants

A remote haploscopic video refractor was used to assess vergence and accommodation responses in a group of 32 emmetropic, orthophoric, symptom free, young adults naïve to vision experiments in a minimally instructed setting. Picture targets were presented at four positions between 2 m and 33 cm. Blur, disparity and looming cues were presented in combination or separately to asses their contributions to the total near response in a within-subjects design. Response gain for both vergence and accommodation reduced markedly whenever disparity was excluded, with much smaller effects when blur and proximity were excluded. Despite the clinical homogeneity of the participant group there were also some individual differences.