Homeostatic plasticity in human extrastriate cortex following a simulated peripheral scotoma

Abstract

Neuroimaging and patient work over the past decade have indicated that, following retinal deafferentation, the human visual cortex undergoes a large-scale and enduring reorganization of its topography such that the classical retinotopic organization of deafferented visual cortex remaps to represent non-classical regions of visual space. Such long-term visual reorganization is proposed to occur through changes in the functional balance of deafferented visual circuits that engage more lasting changes through activity-dependent neuroplasticity. Here, we investigated the short-term changes in functional balance (short-term plasticity; homeostatic plasticity) that occur within deafferented human visual cortices. We recorded electroencephalogram (EEG) while observers were conditioned for 6 s with a simulated retinal scotoma (artificial scotoma) positioned 8.0° in the periphery. Visual evoked potentials (VEPs) evoked by the onset of sinusoidal visual probes that varied in their tilt were used to examine changes in cortical excitability within and around cortical representations of the simulated scotoma. Psychophysical orientation functions obtained from discrimination of visual probe tilt were used to examine alterations in the stimulus selectivity within the scotoma representations. Consistent with a mechanism of homeostatic disinhibition, an early extrastriate component of the VEP (the early phase P1) exhibited increased amplitude following the condition with a simulated scotoma relative to a stimulus-matched control condition. This increased visual cortical response was associated with a reduction in the slope of the psychophysical orientation function, suggesting a broader tuning of neural populations within scotoma representations. Together, these findings support a mechanism of disinhibition in promoting visual plasticity and topographical reorganization.

Tinnitus Perception in Light of a Parietal Operculo–Insular Involvement: A Review

“…In this view, cochlear hair cell impairment is proposed to lead to deafferentation of acoustic nerve fibers, which in turn drives plastic changes within auditory circuits and cortical structures. Similar changes have been described in other sensory modalities, such as in the somatosensory cortex after amputation [7,8] or in the visual cortex following visual field loss [9,10]. In line with these findings, tinnitus perception was therefore suggested to result from maladaptive plasticity similar to the maladaptive plasticity observed in amputees with phantom limb pain [11].…”

Spatiotemporal Dynamics of Covert Attention With Different Degrees of Central Visual Field Defects: An ERP and sLORETA Study

“… 13 Others found the early P1 component of extrastriate generators increased in amplitude in a simulated retinal scotoma relative to healthy controls. 14 Because VEPs can only quantify functional integrity in the retina and early afferent visual pathways, 15 the temporal course of such visual field defects, whether they affect early, lower-level visual processing, or somewhat later, higher-order cognitive processing, is still not fully understood.…”

Investigating the links between spontaneous activity and behaviour in the zebrafish optic tectum

“…Interestingly -and similarly to our findings -some bilateral effects -such as upregulation of certain neurotransmittersare more pronounced following unilateral injury than for bilateral injury. It is also possible that the effect seen in the unilaterally enucleated larvae could represent a mechanism of synaptic compensation, similar to a broadening of orientation tuning observed in cells of the human visual cortex following acute deprivation of visual input in part of one hemifield (Gannon et al, 2017).…”