Biology subjects

Isaacson, J. S.

Publications and source records attributed to Isaacson, J. S..

2 recordsLinked to original sources

bioRxiv2021

Parallel pathways for rapid odor processing in lateral entorhinal cortex: Rate and temporal coding by layer 2 subcircuits

Olfactory information is encoded in lateral entorhinal cortex (LEC) by two classes of layer 2 (L2) principal neurons: fan and pyramidal cells. However, the functional properties of L2 neurons are unclear. Here, we show in awake mice that L2 cells respond rapidly to odors during single sniffs and that LEC is essential for discrimination of odor identity and intensity. Population analyses of L2 ensembles reveals that while rate coding distinguishes odor identity, firing rates are weakly concentration-dependent and changes in spike timing represent odor intensity. L2 principal cells differ in afferent olfactory input and connectivity with local inhibitory circuits and the relative timing of pyramidal and fan cell spikes underlies odor intensity coding. Downstream, intensity is encoded purely by spike timing in hippocampal CA1. Together, these results reveal the unique processing of odor information by parallel LEC subcircuits and highlight the importance of temporal coding in higher olfactory areas.

neuroscience↗

bioRxiv2020

Interhemispheric callosal projections enforce response fidelity and frequency tuning in auditory cortex

Sensory cortical areas receive glutamatergic callosal projections that link information processing between brain hemispheres. However, the role of interhemispheric projections in sensory processing is unclear. Here we use single unit recordings and optogenetic manipulations in awake mice to probe how callosal inputs modulate spontaneous and tone-evoked activity in primary auditory cortex (A1). Although activation of callosal fibers increased firing of some pyramidal cells, the majority of responsive cells were suppressed. In contrast, callosal stimulation consistently increased fast spiking (FS) cell activity and brain slice recordings indicated that parvalbumin (PV)-expressing cells receive stronger callosal input than pyramidal cells or other interneuron subtypes. In vivo silencing of the contralateral cortex revealed that callosal inputs linearly modulate tone-evoked pyramidal cell activity via both multiplicative and subtractive operations. These results suggest that callosal input regulates both the salience and tuning sharpness of tone responses in A1 via PV cell-mediated feedforward inhibition.

neuroscience↗