Biology subjects

Gharaei, S.

Publications and source records attributed to Gharaei, S..

5 recordsLinked to original sources

bioRxiv2026

Cell-type specific inhibitory dynamics shape binocular response normalization in visual cortex

Response normalization during sensory processing is a canonical cortical computation thought to emerge from inhibition-stabilized networks (ISNs). A key prediction from ISNs is that inhibition tracks and scales with excitation, leading to sublinear response summation, but which interneuron classes mediate this operation is unclear. Here, we investigate temporal dynamics and response summation in parvalbumin (PV) and somatostatin (SST) interneurons in mouse binocular visual cortex (bV1). We find that both PV and SST interneurons are binocular but exhibit distinct temporal dynamics and summation profiles. Binocular responses in PV interneurons tracked pyramidal neuron responses, exhibiting sublinear summation consistent with ISN models. In contrast, binocular responses SST interneurons exhibited rapid temporal dynamics and linear or supralinear summation, deviating from ISN predictions. While both PV and SST neurons received excitatory drive via interhemispheric callosal input, they exhibited distinct cellular properties, synaptic dynamics and input-output transformations. Biophysically constrained simulations indicated that cellular and synaptic differences alone were insufficient to reproduce the observed response dynamics in vivo during binocular integration, which were better explained by class-specific differences in local inhibitory circuit motifs. Together, our results indicate that heterogeneous, cell-type-specific inhibitory dynamics shape response normalization in bV1, with PV but not SST interneurons having ISN-like properties.

neuroscience↗

bioRxiv2026

Cortical TRPV1 modulates sensory processing through TRPA1-dependent mechanisms

Transient receptor potential vanilloid 1 (TRPV1) is classically recognised as a peripheral ion channel involved in nociception, but its physiological role in cortical sensory processing remains poorly understood. Here, we investigated whether cortical TRPV1 modulates tactile perception and sensory representations in the vibrissal primary somatosensory cortex (vS1) of mice. TRPV1 activation enhanced perceptual sensitivity, particularly for near-threshold tactile stimuli. In vS1, this was accompanied by stimulus-evoked responses that enhanced stimulus selectivity and discriminability. At the cellular level, activating TRPV1 increased excitability of pyramidal neurons in a TRPA1-dependent manner. Within vS1, TRPV1 activation reduced positive noise correlations and improved stimulus decoding through TRPA1-dependent changes in population activity. Together, these findings identify a TRPV1-TRPA1 signalling mechanism that regulates cortical gain, sharpens sensory representations and enhances perceptual sensitivity. Our results extend the established role of TRPV1 beyond peripheral sensory transduction to central sensory computation.

neuroscience↗

bioRxiv2026

Superior Colliculus Neurons Encode and Causally Shape Sensory Decisions

The ability of an organism to attend to, and orient towards, relevant stimuli is critical for survival. In the mammalian brain, a principal brain region performing this function is the superior colliculus (SC). Despite its important role in attention and orienting movements, little is known about the role the SC plays in sensory decisions. Using Neuropixel recording and optogenetic perturbation of neuronal activity in awake behaving mice, we provide a quantitative link between the activity of neurons in the SC and the behavioural outcome during a whisker-dependent sensory detection task. Consistent with the idea that the SC contributes to sensory decision-making, the activity of SC neurons was correlated with behavioural performance. Furthermore, we found that optogenetic inhibition of the SC reduced behavioural performance without reducing sensitivity or reaction time. These findings indicate that the SC both encodes and causally shapes sensory decisions during a whisker-dependent task.

neuroscience↗

bioRxiv2025

Context Shapes Fear: Habituation of Innate Defensive Behaviours Depends on Environmental Context

The capacity of animals to rapidly and appropriately respond to potential threats is critical for survival. In many species, this involves innate defensive behaviours, such as escape or freezing. But not all threats are dangerous. Habituation - a form of non-associative learning - allows animals to filter out irrelevant stimuli and thereby avoid unnecessary energy expenditure. While it is well known that context can influence behavioural responses to associative learning, whether non-associative forms of learning, such as habituation, are also context-dependent is unclear. Here, we address this issue in mice by examining the role of environmental context on habituation of defensive behaviours to threatening visual stimuli. We first developed a protocol leading to rapid (within minutes) and stable (at least one week) habituation of freezing responses to slowly sweeping visual stimuli, resembling an aerial predator moving across the sky. Using this protocol, we tested the impact of environmental context on habituation of freezing responses, finding that changing the environmental context led to a significant and reversible reduction in habituation. In summary, we find that environmental context plays a critical role in determining the impact of habituation on visually evoked innate defensive behaviours. These findings reveal a previously unrecognised flexibility in defensive responses to visual threats, extending the influence of environmental context to non-associative learning. HighlightsO_LIMice freeze in response to sweeping visual stimuli, resembling an aerial predator. C_LIO_LIHabituation to sweeping visual stimuli could be induced rapidly and remained stable over time. C_LIO_LIHabituation to sweeping visual stimuli depended on environmental context. C_LIO_LIContext-specific habituation was reversible. C_LI

animal behavior and cognition↗

bioRxiv2019

Superior colliculus modulates cortical coding of somatosensory information

The cortex sends a direct projection to the superior colliculus. What is largely unknown is whether (and if so how) the superior colliculus modulates activity in the cortex. Here, we directly investigate this issue, showing that optogenetic activation of superior colliculus changes the input-output relationship of neurons in somatosensory cortex during whisker movement, enhancing responses to low amplitude whisker deflections. While there is no direct pathway from superior colliculus to somatosensory cortex, we found that activation of superior colliculus drives spiking in the posterior medial (POm) nucleus of the thalamus via a powerful monosynaptic pathway. Furthermore, POm neurons receiving input from superior colliculus provide excitatory input to somatosensory cortex. Silencing POm abolished the capacity of superior colliculus to modulate cortical whisker responses. Our findings indicate that the superior colliculus, which plays a key role in attention, modulates sensory processing in somatosensory cortex via a powerful disynaptic pathway through the thalamus.

neuroscience↗