Corticostriatal plasticity is necessary for learning intentional neuroprosthetic skills

Plasticity in the motoro cortices and the striatum has been shown to accompany the learning of physical skills. The motoro cortex and frontal cortices have also been implicated in the learning of abstract skills, and in learning to control neuroprosthetic devices irrespective of physical movement. Some studies suggest that striatum are involved in learning abstract skills as well.

Question Is striatum required for abstract skill earning, and does corticostriatal circuits undergo plasticity during the learning of such skills as they do during the learning of physical skills.

Method

Rats trained to modulate pitch to two different target tones with two ensembles of M1 neurons, increasing firing rates in one ensemble increase the pitch, while the other lowers the pitch. Different rewards associated with reaching target tones.

Manipulation of expected reward values were used to establish causal-relationships.

Findings

  1. Rats showed improved performance through training. Auditory feedback crucial. Not much overt movements during task. Causal-relationship properly demonstrated.

  2. Performance improvements accompanied by significant increase in firing rates in dorsal striatum (DS) in late learning (higher proficiency) compared with early learning.

    DS firing rates exhibited greatest modulation during target reaching compared with baseline control periods, as observed during natural motor learning. Modulation significantly gerater in late learning.

    Indicates DC neurons change activity during volitional control of M1 activity, and the change increases with learning.

    Coherence betweens spiking activity in DS and M1 increases, appeared to be related to learning to performing the task rather than higher reward expectation –> corticostriataal plastiticty important in novel task earning.

  3. Knocked out NMDARs in striatal medium spiny neurons, which are critical for corticostriatal long-term potentiation. Resulting mice weren’t able to learn the neuroprosthetic task.