MEMBRANE-POTENTIAL SYNCHRONY OF SIMULTANEOUSLY RECORDED STRIATAL SPINY NEURONS IN-VIVO

The basal ganglia are an interconnected set of subcortical regions who se established role in cognition and motor control remains poorly unde rstood An important nucleus within the basal ganglia, the striatum, re ceives cortical afferents that convey sensorimotor, limbic and Cogniti ve information(1). The activity of medium-sized spiny neurons in the s triatum seems to depend on convergent input within these information c hannels(2). To determine the degree of correlated input, both below an d at threshold for the generation of action potentials, we recorded in tracellularly from pairs of spiny neurons in vivo. Here we report that the transitions between depolarized and hyperpolarized states were hi ghly Correlated among neurons. Within individual depolarized states, s ome significant synchronous fluctuations in membrane potential occurre d, but action potentials were not synchronized. Therefore, although th e mean afferent signal across fibres is highly correlated among striat al neurons, the moment-to-moment variations around the mean, which det ermine the timing of action potentials, are not. We propose that the p recisely timed, synchronous component of the membrane potential signal s activation of cell assemblies and enables firing to occur. The async hronous component, with low redundancy, determines the fine temporal p attern of spikes.