Representation of the body in the lateral striatum of the freely moving rat: Fast Spiking Interneurons respond to stimulation of individual body parts

Abstract

Numerous studies have shown that certain types of striatal interneurons play a crucial role in selection and regulation of striatal output. Striatal Fast-Spiking Interneurons (FSIs) are parvalbumin positive, GABAergic interneurons that constitute less than 1% of the total striatal population. It is becoming increasingly evident that these sparsely distributed neurons exert a strong inhibitory effect on Medium Spiny projection Neurons (MSNs). MSNs in lateral striatum receive direct synaptic input from regions of cortex representing discrete body parts, and show phasic increases in activity during touch or movement of specific body parts. In the present study, we sought to determine whether lateral striatal FSIs identified by their electrophysiological properties, i.e., short-duration spike and fast firing rate (FR), display body part sensitivity similar to that exhibited by MSNs. During video recorded somatosensorimotor exams, each individual body part was stimulated and responses of single neurons were observed and quantified. Individual FSIs displayed patterns of activity related selectively to stimulation of a discrete body part. Most patterns of activity were similar to those exhibited by typical MSNs, but some phasic decreases were observed. These results serve as evidence that some striatal FSIs process information related to discrete body parts and participate in sensorimotor processing by striatal networks that contribute to motor output.

Homogeneous processing in the striatal direct and indirect pathways: single body part sensitive type IIb neurons may express either dopamine receptor D1 or D2

“…No such result has ever been reported; on the contrary, specificity of phasic firing in relation to movement around an individual joint is similar between GPi and GPe neurons (Iansek & Porter, ; Erez et al ., ) and is lost only in disease models (Filion et al ., ; Rothblat & Schneider, ). We have recently suggested that, alternatively, maintaining low FR of MSNs that are unrelated to the current movement may involve striatal fast spiking interneurons that respond to individual body parts (Kulik et al ., ).…”

A biophysical model of striatal microcircuits suggests gamma and beta oscillations interleaved at delta/theta frequencies mediate periodicity in motor control

“…Coordinated FSI activity has proven hard to observe over long periods in vivo [14,118]. However, FSIs form local functional circuits [119], and in vivo, striatal FSI assemblies exhibit transient gap-junction dependent synchronization [66], possibly resulting from brief bouts of correlated cortical or homogeneous DAergic input. Furthermore, different subpopulations of FSIs have strong preferences for projecting to either D1 or D2 SPNs, as opposed to the overlapping projections modeled in our current study, and these distinct populations respond differently to cortical oscillations [80].…”

A Cortical Pathogenic Theory of Parkinson’s Disease

“…Nigrostriatal input exerts not only the classic receptor-dependent post-synaptic neuromodulation of MSN excitability (Gerfen and Surmeier, 2011), but also pre-synaptic inhibition of glutamate striatal release via dopaminergic receptors on corticostriatal terminals in an activity-dependent fashion (Bamford et al, 2004). MSN excitability is also influenced and modulated by striatal cholinergic and GABAergic interneurons (Tepper et al, 2004;Faust et al, 2016), which control striatal output activity particularly in the sensorimotor striatum (Kulik et al, 2017) and are also modulated by dopaminergic input (Momiyama and Nishijo, 2017). Altogether, corticostriatal and nigrostriatal axons interact at the synaptic level forming a functional unit with MSNs and interneurons (Shipp, 2017).…”