Biology subjects

Schmehl, M. N.

Publications and source records attributed to Schmehl, M. N..

2 recordsLinked to original sources

bioRxiv2024

Visually-evoked activity and variable modulation of auditory responses in the macaque inferior colliculus

How multisensory cues affect processing in early sensory brain areas is not well understood. The inferior colliculus (IC) is an early auditory structure that is visually responsive (Porter et al. 2007; Bulkin and Groh 2012a, 2012b), but little is known about how visual signals affect the ICs auditory representation. We explored how visual cues affect both spiking and local field potential (LFP) activity in the IC of two monkeys performing a task involving saccades to auditory, visual, or combined audiovisual stimuli. We confirm that LFPs are sensitive to the onset of fixation lights as well as the onset of visual targets presented during steady fixation. The LFP waveforms evoked by combined audiovisual stimuli differed from those evoked by sounds alone. In single-unit spiking activity, responses were weak when visual stimuli were presented alone, but visual stimuli could modulate the activity evoked by sounds in a stronger way. Such modulations could involve either increases or decreases in activity, and whether increases or decreases were observed was variable and not obviously correlated with the responses evoked by visual or auditory stimuli alone. These findings indicate that visual stimuli shape the ICs auditory representation in flexible ways that differ from those observed previously in multisensory areas. New & NoteworthyWe find that the inferior colliculus, a primarily auditory brain area, displays distinct population-level responses to visual stimuli. We also find that visual cues can influence the auditory responses of individual neurons. Together, the results provide insight into how relatively early sensory areas may play a role in combining multiple sensory modalities to refine the perception of complex environments.

neuroscience↗

bioRxiv2023

Multiple objects evoke fluctuating responses in several regions of the visual pathway

How neural representations preserve information about multiple stimuli is mysterious. Because tuning of individual neurons is coarse (for example, visual receptive field diameters can exceed perceptual resolution), the populations of neurons potentially responsive to each individual stimulus can overlap, raising the question of how information about each item might be segregated and preserved in the population. We recently reported evidence for a potential solution to this problem: when two stimuli were present, some neurons in the macaque visual cortical areas V1 and V4 exhibited fluctuating firing patterns, as if they responded to only one individual stimulus at a time (Jun et al., 2022). However, whether such an information encoding strategy is ubiquitous in the visual pathway and thus could constitute a general phenomenon remains unknown. Here we provide new evidence that such fluctuating activity is also evoked by multiple stimuli in visual areas responsible for processing visual motion (middle temporal visual area, MT), and faces (middle fundus and anterolateral face patches in inferotemporal cortex - areas MF and AL), thus extending the scope of circumstances in which fluctuating activity is observed. Furthermore, consistent with our previous results in the early visual area V1, MT exhibits fluctuations between the representations of two stimuli when these form distinguishable objects but not when they fuse into one perceived object, suggesting that fluctuating activity patterns may underlie visual object formation. Taken together, these findings point toward an updated model of how the brain preserves sensory information about multiple stimuli for subsequent processing and behavioral action. Impact StatementNeural fluctuations in multiple areas along the visual cortical hierarchy could allow the brain to represent distinct co-occurring visual stimuli.

neuroscience↗