Local feedback inhibition tightly controls rapid formation of hippocampal place fields

Multiscale and Extended Retrieval of Associative Memory Structures in a Cortical Model of Local-Global Inhibition Balance

“…However, using disinhibition, this effect can be nullified and the neural assemblies can be made larger. Rolotti et al (2022) showed such disinhibition can improve performance on a head-fixed spatial goal-oriented learning task via overrepresentation of the rewarded locations used for performance in the task. Another functional benefit of such disinhibition may be in rapid place field formation, as is seen in the behavioral timescale synaptic plasticity mechanism ( Bittner et al, 2017 ; Zhao et al, 2020 ; Milstein et al, 2021 ).…”

“…Recent experimental evidence in mice ( Rolotti et al, 2022 ) shows that when optogenetic techniques are used to induce place field formation in CA1 neurons, feedback inhibition limits the number of neurons which become activated, thereby limiting the size of the neural assembly which becomes activated by the induced place field. However, using disinhibition, this effect can be nullified and the neural assemblies can be made larger.…”

“…In Rolotti et al (2022) , the feedback inhibition comes from the hippocampus, but they do not explore distinctions between different inhibitory populations therein. There are many different types of inhibitory neurons, each with distinct connectivity, dynamics, and morphology ( Pelkey et al, 2017 ; Burns and Rajan, 2021 ; Campagnola et al, 2022 ).…”

“…We treat neurons as having a single point of intracellular space, i.e., without dendrites or specific morphology, which other than itself being unrealistic also prevents us from allowing different classes of inhibitory neurons to preferentially synapse onto different regions of other neurons, which is known to vary widely across inhibitory neurons ( Otsuka and Kawaguchi, 2009 ; Burns and Rajan, 2021 ; Dudok et al, 2021 ). We also assume that joint excitatory-inhibitory assemblies are completely connected, which is a simplification that does not match biology ( Otsuka and Kawaguchi, 2009 ; Koolschijn et al, 2019 ; Rolotti et al, 2022 ). Therefore, these and other limitations mean that whether and how actual biological networks achieve the same functional benefits we described here using inhibitory neuron diversity currently remains unknown.…”

Advantages, Pitfalls, and Developments of All Optical Interrogation Strategies of Microcircuits in vivo

“…In all optical physiology, in some cases, it can be physiologically relevant to photostimulate a high number of cells, in particular when aiming to replicate spontaneous patterns on a mesoscale level [although there are clear evidences that the number of neurons necessary to elicit a perception is in the order of a dozen in the visual cortex ( Dalgleish et al, 2020 ), of 20 in the olfactory bulb ( Gill et al, 2020 ), on top of observations indicating the existence of possibly supralinear inhibitory mechanisms limiting the activated/activable area ( Rolotti et al, 2022 )]. This can be achieved by using lasers with higher peak powers (and lower repetition rate to maintain the average power within biologically safe limits).…”