Contrast adaptation in cat lateral geniculate nucleus and influence of corticothalamic feedback

Abstract

Contrast adaptation is a basic property of visual information processing. However, important questions about contrast adaptation in the lateral geniculate nucleus (LGN) remain. For example, it is unclear whether the different information channels have the same or distinct contrast adaptation properties and mechanisms. It has been recognized that the visual system is not a one-way ascending pathway, but also contains descending feedback projections. Although studies have explored the role of this feedback system, it is unclear whether corticothalamic feedback contributes to adaptation in the LGN. To investigate these questions, we studied contrast adaptation of LGN neurons in anesthetized and paralysed cats by measuring electrophysiological responses to visual test stimuli before and after adaptation induced by prolonged visual stimulation. After adaptation, contrast response functions were usually shifted towards higher contrasts, indicating decreased contrast gain, and the maximum response decreased. Also, contrast adaptation effects were stronger in Y-cells than in X-cells. Furthermore, adaptation effects were still observed in the LGN when the corticothalamic feedback was inactivated. Changes in the contrast gain of Y-cells were diminished in the absence of feedback, while contrast gain was largely unchanged in X-cells. Our observations confirm that contrast adaptation occurs in LGN neurons and furthermore demonstrate that Y-cells show stronger adaptation effects than X-cells. These results also provide an example of how corticothalamic feedback modulates contrast information processing distinctly in different information channels.

Corticogeniculate feedback sharpens the temporal precision and spatial resolution of visual signals in the ferret

“…Indeed, numerous studies using a variety of experimental techniques to manipulate CG feedback have documented changes in the magnitude of LGN responses (7)(8)(9)(10)(11)(12)(13)(14). Our results are consistent with some, but not all, of these observations.…”

“…We did not observe systematic increases or decreases in contrast response magnitude in LGN X or Y neurons (similarly, we did not observe systematic magnitude modulation of spatial frequency responses), more consistent with the findings in the mouse visual system. Notably, some of the previously observed contrast gain changes were specific to particular LGN cell types, for example parvocellular neurons in monkey LGN (13) and Y neurons in cat LGN (10). We also observed larger increases in the magnitude of temporal frequency responses for LGN Y neurons compared with X neurons.…”

“…Some have proposed that CG feedback modulates the gain (7)(8)(9)(10)(11)(12)(13)(14) and/or the spatiotemporal properties of LGN neurons (15)(16)(17). Others have proposed that corticothalamic feedback controls whether thalamic neurons are in a state of net excitation or inhibition (8,12), depending upon oscillatory activity in corticothalamic networks (18).…”

A brief review on current progress in neuroscience in China

“…Some other investigations have tried to reveal the neural mechanism of vision-related cognitive functions at the cellular level, and have elucidated the role of two pairs of neurons in the central nervous system which control Drosophila initiate light preference [38], contrast pattern and contrast adaption of perceptual learning and temporal and spatial patterns of retinal ganglion cells in response to natural stimuli [39][40][41], sexual difference of aging-associated functional degradation in visual cortical cells [42].…”

Role of EphA/ephrin‐A signaling in the development of topographic maps in mouse corticothalamic projections

“…CT projections comprise almost 50% of the synaptic input onto thalamic sensory neurons and are ∼10‐fold more abundant than TC projections (Jones, 2002). This massive CT feedback dynamically influences thalamic processing of sensory information by sharpening the receptive fields and/or shifting the tuning of thalamic neurons, as well as enhancing or suppressing the transmission of sensory signals from the periphery to the cortex (Lee et al, 2008;Briggs and Usrey, 2008, 2009;Kondo and Kashino, 2009;Li et al, 2011;Paz et al, 2011;Olsen et al, 2012). Such intimate functional interconnection largely depends on the high degree of reciprocity in neural circuits that connect the thalamus and cerebral cortex (Temereanca and Simons, 2004).…”