Biology subjects

Marchesi, P.

Publications and source records attributed to Marchesi, P..

4 recordsLinked to original sources

bioRxiv2023

Neural correlates of object identity and reward outcome in the corticohippocampal hierarchy: double dissociation between perirhinal and secondary visual cortex

Neural circuits support behavioral adaptations by integrating sensory and motor information with reward and error-driven learning signals, but it remains poorly understood how these signals are distributed across different levels of the corticohippocampal hierarchy. We trained rats on a multisensory object-recognition task and compared visual and tactile responses of simultaneously recorded neuronal ensembles in somatosensory cortex, secondary visual cortex, perirhinal cortex and hippocampus. The sensory regions primarily represented unisensory information, while hippocampus was modulated by both vision and touch. Surprisingly, secondary visual cortex but not perirhinal neurons coded object-specific information, whereas perirhinal but not visual cortical neurons signaled trial outcome. A majority of outcome-related perirhinal cells responded to a negative outcome (reward omission), whereas a minority of other cells coded positive outcome (reward delivery). Our results support a distributed neural coding of multisensory variables in the cortico-hippocampal hierarchy, with a double dissociation between higher visual cortex and perirhinal cortex in coding of object identity versus feedback on trial outcome.

animal behavior and cognition↗

bioRxiv2022

Triple dissociation of visual, auditory and motor processing in primary visual cortex

Primary sensory cortices respond to crossmodal stimuli, for example auditory responses are found in primary visual cortex (V1). However, it remains unclear whether these responses reflect sensory inputs or behavioural modulation through sound-evoked body movement. We address this controversy by showing that sound-evoked activity in V1 of awake mice can be dissociated into auditory and behavioural components with distinct spatiotemporal profiles. The auditory component began at [~]27 ms, was found in superficial and deep layers and originated from auditory cortex, as shown by inactivation by muscimol. Sound-evoked orofacial movements correlated with V1 neural activity starting at [~]80-100 ms and explained auditory frequency-tuning. Visual, auditory and motor activity were expressed by segregated neuronal populations and during simultaneous audiovisual stimulation, visual representations remained dissociable from auditory and motor-related activity. This threefold dissociability of auditory, motor and visual processing is central to understanding how distinct inputs to visual cortex interact to support vision.

neuroscience↗

bioRxiv2021

Coherent mapping of position and head direction across auditory and visual cortex

Neurons in primary visual cortex (V1) may not only signal current visual input but also relevant contextual information such as reward expectancy and the subjects spatial position. Such location-specific representations need not be restricted to V1 but could participate in a coherent mapping throughout sensory cortices. Here we show that spiking activity in primary auditory cortex (A1) and lateral, secondary visual cortex (V2L) of freely moving rats coherently represents a location-specific mapping in a sensory detection task performed on a figure-8 maze. Single-unit activity of both areas showed extensive similarities in terms of spatial distribution, reliability and position coding. Importantly, reconstructions of subject position on the basis of spiking activity displayed decoding errors that were correlated between areas in magnitude and direction. In addition to position, we found that head direction, but not locomotor speed or head angular velocity, was an important determinant of activity in A1 and V2L. Finally, pairs of units within and across areas showed significant correlations in instantaneous variability of firing rates (noise correlations). These were dependent on the spatial tuning of cells as well as the spatial position of the animal. We conclude that sensory cortices participate in coherent, multimodal representations of the subjects sensory-specific location. These may provide a common reference frame for distributed cortical sensory and motor processes and may support crossmodal predictive processing.

neuroscience↗

bioRxiv2021

Task complexity temporally extends the causal requirement for visual cortex in perception

The transformation of sensory inputs into behavioral outputs is characterized by an interplay between feedforward and feedback operations in cortical hierarchies. Even in simple sensorimotor transformations, recurrent processing is often expressed in primary cortices in a late phase of the cortical response to sensory stimuli. This late phase is engaged by attention and stimulus complexity, and also encodes sensory-independent factors, including movement and report-related variables. However, despite its pervasiveness, the nature and function of late activity in perceptual decision-making remain unclear. We tested whether the function of late activity depends on the complexity of a sensory change-detection task. Complexity was based on increasing processing requirements for the same sensory stimuli. We found that the temporal window in which V1 is necessary for perceptual decision-making was extended when we increased task complexity, independently of the presented visual stimulus. This window overlapped with the emergence of report-related activity and decreased noise correlations in V1. The onset of these co-occurring activity patterns was time-locked to and preceded reaction time, and predicted the reduction in behavioral performance obtained by optogenetically silencing late V1 activity (>200 ms after stimulus onset), a result confirmed by a second multisensory task with different requirements. Thus, although early visual response components encode all sensory information necessary to solve the task, V1 is not simply relaying information to higher-order areas transforming it into behavioral responses. Rather, task complexity determines the temporal extension of a loop of recurrent activity, which overlaps with report-related activity and determines how perceptual decisions are built.

neuroscience↗