Information Processing in the Striatum of Behaving Monkeys
Neuronal signals in the cerebral cortex are sent to the striatum, which is a major input structure of the basal ganglia. The striatum contains GABAergic spiny projection neurons and interneurons. Projection neurons, which receive excitatory glutamatergic inputs from the cortex and thalamus through both NMDA and AMPA/kainate receptors, have extensive local axon collaterals that form synapses with other neighboring projection neurons. GABAergic interneurons receive cortical inputs and innervate projection neurons. Thus, the activity of projection neurons is thought to be controlled by such GABAergic networks in the striatum. To investigate the functions of GABAergic networks, we recorded the activity of striatal projection neurons in behaving monkeys during performance of a reaching task with delay under the blockade of GABAergic and glutamatergic neurotransmission. Injection of a GABAA receptor blocker, gabazine, in the vicinity of the recorded neurons enhanced cortically evoked responses and task-related activity. Additional injection of glutamatergic blockers (a mixture of an NMDA receptor blocker, CPP and an AMPA/kainate receptor blocker, NBQX) diminished both cortically evoked responses and task-related activity to almost zero. These results suggest that the activity of striatal projection neurons is (1) mainly governed by the cortical inputs and (2) modified or adjusted by GABAergic networks in the striatum.
KeywordsProjection Neuron GABAergic Interneuron Medium Spiny Neuron Cortical Input Feedforward Inhibition
- Bennett BD and Wilson CJ (2000) Synaptology and physiology of neostriatal neurones. In: Miller R and Wickens JR (eds) Brain Dynamics and the Striatal Complex. Harwood Academic Publishers, Amsterdam. pp 111–140.Google Scholar
- Takara S, Hatanaka N, Takada M and Nambu A (2006) Activity of putaminal neurons receiving inputs from motor cortical areas in behaving monkeys. Neurosci Res 55: S247.Google Scholar