Biology subjects

Kermani, M.

Publications and source records attributed to Kermani, M..

3 recordsLinked to original sources

bioRxiv2020

Long-range neural coherence encodes stimulus information in primate visual cortex

In the primary visual cortex, neurons with similar receptive field properties are bound together through widespread networks of horizontal connections that span orientation columns. How connectivity across the cortical surface relates to stimulus information is not fully understood. We recorded spiking activity and the local field potential (LFP) from the primary visual cortex of marmoset monkeys and examined how connectivity between distant orientation columns affect the encoding of visual orientation. Regardless of their spatial separation, recording sites with similar orientation preferences have higher coherence between spiking activity and the local field potential than sites with different preferred orientation. Using information theoretic methods, we measured the amount of stimulus information that is shared between pairs of sites. More stimulus information can be decoded from pairs with the same preferred stimulus orientation than the pairs with a different preferred orientation, and the amount of information is significantly correlated with the magnitude of beta-band spike-LFP coherence. These effects remained after controlling for firing rate differences. Our results thus show that spike-LFP synchronization in the beta-band is associated with the encoding of stimulus information within the primary visual cortex of marmoset monkeys. Significance StatementA fundamental step in processing images in the visual cortex is coordinating the neural activity across distributed populations of neurons. Here, we demonstrate that populations of neurons in the primary visual cortex of marmoset monkeys with the same stimulus orientation preference temporally coordinate their activity patterns when presented with a visual stimulus. We find maximum synchronization in the beta range depends on the similarity of orientation preference at each pair of the neural population.

neuroscience↗

bioRxiv2020

Effects of Antipsychotic Drugs and Potassium Channel Modulators on Cognition-related Local Field Potential Spectral Properties in Mouse Hippocampus and Frontal Cortex

Local field potentials (LFPs) recorded intracranially display a range of location specific oscillatory spectra which have been related to cognitive processes. Although the exact mechanisms producing LFPs are not completely understood, it is likely that voltage-gated ion channels which produce action potentials and patterned discharges play a significant role. It is also known that antipsychotic drugs (APDs) affect LFPs spectra and a direct inhibitory effect on voltage-gated potassium (Kv) channels has been reported. Additionally, Kv channels have been implicated in the pathophysiology of schizophrenia, a disorder for which APDs are primary therapies. In this study we sought to: i) better characterise the effects of two APDs on LFPs and connectivity measures and ii) examine the effects of potassium channel modulators on LFPs and potential overlap of effects with APDs. Intracranial electrodes were implanted in the hippocampus (HIP) and pre-frontal cortex (PFC) of C57BL/6 mice; power spectra, coherence and phase-amplitude cross frequency coupling were measured. Drugs tested were the APDs haloperidol and clozapine as well as voltage-gated potassium channel modulators (KVMs) 4-aminopyridine(4AP), tetraethylammonium (TEA), E-4031 and retigabine. All drugs and vehicle controls were administered intraperitoneally. Both APDs and KVMs significantly reduced gamma power with the exception of 4AP, which conversely increased slow-gamma power. Clozapine and retigabine additionally reduced coherence between HIP and PFC. Phase-amplitude coupling between theta and gamma oscillations in HIP was significantly reduced by the administration of haloperidol and retigabine. These results provide previously undescribed effects of APDs on LFP properties and demonstrate novel modulation of LFP characteristics by KVMs that intriguingly overlaps with the effects of APDs. The possibility of a common mechanism of action deserves further study.

neuroscience↗

bioRxiv2020

Dynamics of coherent activity between cortical areas defines a two-stage process of selective attention

Analysing a visual scene requires the brain to briefly keep in memory potentially relevant parts and then direct attention to their locations for detailed processing. To reveal the neuronal basis of the underlying working memory and top-down attention processes, we trained macaques to match two patterns presented with a delay between them. As the above processes are likely to require communication between brain regions, and the parietal cortex is involved in spatial attention, we simultaneously recorded neuronal activities from the interconnected parietal and middle temporal areas. We found that mnemonic information about the first pattern was retained in coherent oscillating activity between the areas in high-frequency bands, followed by coherent activity in low-frequency bands that mediate top-down attention on the relevant location. ONE SENTENCE SUMMARYGamma coherence allows retaining object features in a saliency map while lower frequency coherence facilitates attention.

neuroscience↗