Biology subjects

Karlocai, M. R.

Publications and source records attributed to Karlocai, M. R..

3 recordsLinked to original sources

bioRxiv2026

The Amygdalostriatal Transition Area Exhibits Lateral Amygdala-Like Spiking Activity and Tone-Shock Pairing-Induced Plasticity

During Pavlovian fear conditioning, presentation of a conditioned stimulus, such as a tone, together with an unconditioned stimulus, such as an electrical shock, excites neurons in the lateral amygdala (LA). Prevailing models propose that sensory stimulus-evoked activity in the LA is subsequently propagated to its downstream nuclei: the basal amygdala (BA) and central amygdala (CeA). To test this assumption, we performed in vivo electrophysiological recordings in awake, head-fixed male and female mice. We found that tone presentation did not elicit a significant increase in firing in BA or CeA neurons. In contrast, shock presentation evoked similarly robust spiking responses in LA and BA neurons but only a modest increase in CeA neurons. Notably, neurons in the amygdalostriatal transition area (AStria) exhibited LA-like sensory stimulus-evoked responses at both short (<25 ms) and longer (<500 ms) timescales. To examine the role of feedforward inhibition in tone- and shock-evoked activity, we investigated the contribution of parvalbumin interneurons using optogenetics and found that short-latency (<25 ms) spiking in both the LA and AStria was regulated by these inhibitory cells. Finally, LA and AStria neurons exhibited remarkably similar response types, spiking dynamics, and pairing-induced plasticity during repeated tone presentations, subsequent tone-shock pairings, and post-pairing tone presentations. Together, these findings support a model in which the LA and AStria operate in parallel, similarly integrating tone and shock signals during fear conditioning, whereas BA and CeA neurons are not robustly recruited by these sensory stimuli under the conditions tested.

neuroscience↗

bioRxiv2023

Structural organisation of perisomatic inhibition in the mouse medial prefrontal cortex

Perisomatic inhibition profoundly controls neural function. However, the structural organisation of inhibitory circuits giving rise to the perisomatic inhibition in the higher-order cortices is not completely known. Here, we performed a comprehensive analysis of those GABAergic cells in the medial prefrontal cortex (mPFC) that provide inputs onto the somata and proximal dendrites of pyramidal neurons. Our results show that most GABAergic axonal varicosities contacting the perisomatic region of superficial (layer 2/3) and deep (layer 5) pyramidal cells express parvalbumin (PV) or cannabinoid receptor type 1 (CB1). Further, we found that the ratio of PV/CB1 GABAergic inputs is larger on the somatic membrane surface of pyramidal tract neurons in comparison to those projecting to the contralateral hemisphere. Our morphological analysis of in vitro labelled PV+ basket cells (PVBC) and CCK/CB1+ basket cells (CCKBC) revealed differences in many features. PVBC dendrites and axons arborized preferentially within the layer where their soma was located. In contrast, the axons of CCKBCs expanded throughout layers, though their dendrites were found preferentially either in superficial or deep layers. Finally, using anterograde trans-synaptic tracing we observed that PVBCs are preferentially innervated by thalamic and basal amygdala afferents in layer 5a and 5b, respectively. Thus, our results suggest that PVBCs can control the local circuit operation in a layer-specific manner via their characteristic arborization, while CCKBCs rather provide cross-layer inhibition in the mPFC. Significance StatementInhibitory cells in cortical circuits are crucial for the precise control of local network activity. Nevertheless, in higher-order cortical areas that are involved in cognitive functions like decision making, working memory and cognitive flexibility, the structural organisation of inhibitory cell circuits is not completely understood. In this study we show that perisomatic inhibitory control of excitatory cells in the medial prefrontal cortex is performed by two types of basket cells endowed with different morphological properties that provide inhibitory inputs with distinct layer specificity on cells projecting to disparate areas. Revealing this difference in innervation strategy of the two basket cell types is a key step towards understanding how they fulfil their distinct roles in cortical network operations.

neuroscience↗

bioRxiv2021

Hippocampal sharp wave-ripples and the associatedsequence replay emerge from structured synapticinteractions in a network model of area CA3

Hippocampal place cells are activated sequentially as an animal explores its environment. These activity sequences are internally recreated ("replayed"), either in the same or reversed order, during bursts of activity (sharp wave-ripples; SWRs) that occur in sleep and awake rest. SWR-associated replay is thought to be critical for the creation and maintenance of long-term memory. In order to identify the cellular and network mechanisms of SWRs and replay, we constructed and simulated a data-driven model of area CA3 of the hippocampus. Our results show that the chain-like structure of recurrent excitatory interactions established during learning not only determines the content of replay, but is essential for the generation of the SWRs as well. We find that bidirectional replay requires the interplay of the experimentally confirmed, temporally symmetric plasticity rule, and cellular adaptation. Our model provides a unifying framework for diverse phenomena involving hippocampal plasticity, representations, and dynamics, and suggests that the structured neural codes induced by learning may have greater influence over cortical network states than previously appreciated.

neuroscience↗