The main model of visual processing in primates proposes an anatomo-functional distinction between the dorsal stream, specialized in spatio-temporal information, and the ventral stream, processing ...essentially form information. However, these two pathways also communicate to share much visual information. These dorso-ventral interactions have been studied using form-from-motion (FfM) stimuli, revealing that FfM perception first activates dorsal regions (e.g., MT+/V5), followed by successive activations of ventral regions (e.g., LOC). However, relatively little is known about the implications of focal brain damage of visual areas on these dorso-ventral interactions. In the present case report, we investigated the dynamics of dorsal and ventral activations related to FfM perception (using topographical ERP analysis and electrical source imaging) in a patient suffering from a deficit in FfM perception due to right extrastriate brain damage in the ventral stream. Despite the patient’s FfM impairment, both successful (observed for the highest level of FfM signal) and absent/failed FfM perception evoked the same temporal sequence of three processing states observed previously in healthy subjects. During the first period, brain source localization revealed cortical activations along the dorsal stream, currently associated with preserved elementary motion processing. During the latter two periods, the patterns of activity differed from normal subjects: activations were observed in the ventral stream (as reported for normal subjects), but also in the dorsal pathway, with the strongest and most sustained activity localized in the parieto-occipital regions. On the other hand, absent/failed FfM perception was characterized by weaker brain activity, restricted to the more lateral regions. This study shows that in the present case report, successful FfM perception, while following the same temporal sequence of processing steps as in normal subjects, evoked different patterns of brain activity. By revealing a brain circuit involving the most rostral part of the dorsal pathway, this study provides further support for neuro-imaging studies and brain lesion investigations that have suggested the existence of different brain circuits associated with different profiles of interaction between the dorsal and the ventral streams.
Highlights • Aging in monkeys has an effect on the visual system. • Neuronal baseline activity does not change with aging in the inferotemporal cortex (IT). • Neuronal latency values in the IT ...increase with age. • Variables reflecting stimulus preference in IT change in a way which indicates decreased stimulus selectivity for visual neurons.
Within the last five years, there have been a number of exciting new advances in our knowledge and understanding of amblyopia. This article reviews recent psychophysical studies of naturally ...occurring amblyopia in humans. These studies suggest that: 1) There are significant differences in the patterns of visual loss among the clinically defined categories of amblyopes. A key factor in determining the nature of the loss is the presence or absence of binocularity. 2) Dysfunction within the amblyopic visual system first occurs in area V1, and the effects of amblyopia may be amplified downstream. 3) There appears to be substantial neural plasticity in the amblyopic brain beyond the "critical period."
Aim. A high rate of abnormal social behavioural traits or perceptual deficits is observed in children with unilateral temporal lobe epilepsy. In the present study, perception of auditory and visual ...social signals, carried by faces and voices, was evaluated in children or adolescents with temporal lobe epilepsy.
Methods. We prospectively investigated a sample of 62 children with focal non‐idiopathic epilepsy early in the course of the disorder. The present analysis included 39 children with a confirmed diagnosis of temporal lobe epilepsy. Control participants (72), distributed across 10 age groups, served as a control group. Our socio‐perceptual evaluation protocol comprised three socio‐visual tasks (face identity, facial emotion and gaze direction recognition), two socio‐auditory tasks (voice identity and emotional prosody recognition), and three control tasks (lip reading, geometrical pattern and linguistic intonation recognition). All 39 patients also benefited from a neuropsychological examination.
Results. As a group, children with temporal lobe epilepsy performed at a significantly lower level compared to the control group with regards to recognition of facial identity, direction of eye gaze, and emotional facial expressions. We found no relationship between the type of visual deficit and age at first seizure, duration of epilepsy, or the epilepsy‐affected cerebral hemisphere. Deficits in socio‐perceptual tasks could be found independently of the presence of deficits in visual or auditory episodic memory, visual non‐facial pattern processing (control tasks), or speech perception. A normal FSIQ did not exempt some of the patients from an underlying deficit in some of the socio‐perceptual tasks.
Conclusion. Temporal lobe epilepsy not only impairs development of emotion recognition, but can also impair development of perception of other socio‐perceptual signals in children with or without intellectual deficiency. Prospective studies need to be designed to evaluate the results of appropriate re‐education programs in children presenting with deficits in social cue processing.
In the past five years, substantial progress has been made in our knowledge of the neural basis of amblyopia. Recent advances based on animal models are described, along with new psychophysical data ...showing perceptual deficits in amblyopic animals that are not explained by simple losses in contrast sensitivity. Studies of contour integration and integration of motion and form signals in the presence of noise show that 1) there are fundamental losses in temporal as well as spatial vision, 2) the losses extend to the fellow eye in many cases, 3) amblyopic animals are especially impaired in the presence of background noise, and 4) these losses must depend on a process downstream from area V1 in the extrastriate cortex.
Abstract Objective We describe a patient with prodromal dementia with Lewy bodies (DLB) presenting with drug-induced visual hallucinations (VHs). Case report A 78-year-old woman complained of daytime ...recurrent VHs characterized by seeing her face and arms covered in fur and viewing moustaches on her daughter's face. VHs started a few days after the beginning of a combination therapy with duloxetine and lorazepam and ceased within 24 h after their discontinuation. Nonamnestic mild cognitive impairment with profound visual perception deficits and very mild extrapyramidal signs, with abnormal brain DaTscan single photon emission tomography, were present. Three years later, cognitive and neurological follow-up assessments supported the diagnosis of DLB. Conclusion Perturbation of cerebral serotonergic tone induced by duloxetine, associated with reduced attentional control due to benzodiazepine use, may be the physiopathological substrate of transient VHs in prodromal DLB.
Two experiments examined how sensory acuity affects age differences in susceptibility to interference in the reading-with-distraction task. In both experiments, older and younger adults read texts in ...an italic font and were required to ignore distractor words in an upright font. Experiment 1 examined whether the age-related increase in distractibility can be simulated in younger adults by reducing their visual acuity. Experiment 2 investigated whether the age differences in distractibility disappear if visual acuity is equated across all participants in both age groups. Both experiments showed that an impairment in visual acuity leads to increased interference in the reading-with-distraction task. However, older adults were much more impaired by the distractor material than younger adults with reduced visual acuity (Experiment 1). The age differences in the reading-with-distraction task persisted when visual acuity was equated between older and younger adults (Experiment 2). We conclude that the age-related increase in susceptibility to interference in the reading-with-distraction task is not solely due to perceptual deficits of older adults but arises from a deficit in higher cognitive processes such as inhibitory attention. Nevertheless, sensory acuity has to be taken into account as a potential confounding factor in perceptually demanding visual attention tasks.
Body image research with young children has typically examined their body satisfaction and overlooked developmental theories pertaining to their emergent body-knowledge. Though existing research ...suggests that preschoolers do demonstrate anti-fat attitudes and weight-related stigmatisation, body dissatisfaction can be difficult to assess in preschoolers due to developmental differences in their (i) ability to perceive their actual body size accurately and (ii) make comparisons with a hypothetical ideal. We review current findings on the attitudinal component of body image in preschoolers, together with findings on the accuracy of their body size perceptions and their emergent body awareness abilities. Such an integration of the cognitive development literature is key to identifying when and how young children understand their physical size and shape; this in turn is critical for informing methodological design targeted at assessing body dissatisfaction and anti-fat attitudes in early childhood.
AH, a young, well-educated woman, has a developmental deficit in processing visual location and orientation information. Her deficit manifests itself in a wide range of visual tasks, including ...visually-guided reaching, copying pictures and words, and responding verbally to the location or orientation of visual stimuli; however, her performance in non-visual localization tasks is intact. AH's visual location and orientation errors are systematic left-right or up-down reflections (e.g., reaching to the far right for an object on the far left). More specifically, the errors involve reflection across the point where AH's attention is focused, regardless of where her eyes are fixated. These results imply that at some level(s) of the visual system, locations and orientations of visual stimuli are represented in a spatial coordinate system with an origin defined by the focus of attention. In these attention-centered representations location is specified in terms of distance and direction of displacement from the attentional focus along horizontal and vertical reference axes. AH's errors, I argue, result from mis-representation of displacement direction (e.g., left rather than right, down rather than up) along a reference axis. Several visual variables dramatically affected AH's performance in visual location and orientation tasks: She was much more accurate for stimuli that were brief, moving, flickering, low in contrast, or high in eccentricity, than for those that were long in duration, stationary, continuous, high in contrast, and low in eccentricity. These results suggest that location and orientation are computed in each of two visual subsystems, which I call transient and sustained, and that AH's deficit affects only the sustained subsystem. I argue that AH's performance poses challenges to multiple-visual-subsystems hypotheses proposed by Ungerleider and Mishkin (1982) and by Milner and Goodale (1995).
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