Biomedical subjects

Jaideep Mavoori

Publications and source records attributed to Jaideep Mavoori.

4 recordsLinked to original sources

PubMed2006

Long-term motor cortex plasticity induced by an electronic neural implant.

It has been proposed that the efficacy of neuronal connections is strengthened when there is a persistent causal relationship between presynaptic and postsynaptic activity. Such activity-dependent plasticity may underlie the reorganization of cortical representations during learning, although direct in vivo evidence is lacking. Here we show that stable reorganization of motor output can be induced by an artificial connection between two sites in the motor cortex of freely behaving primates. An autonomously operating electronic implant used action potentials recorded on one electrode to trigger electrical stimuli delivered at another location. Over one or more days of continuous operation, the output evoked from the recording site shifted to resemble the output from the corresponding stimulation site, in a manner consistent with the potentiation of synaptic connections between the artificially synchronized populations of neurons. Changes persisted in some cases for more than one week, whereas the output from sites not incorporated in the connection was unaffected. This method for inducing functional reorganization in vivo by using physiologically derived stimulus trains may have practical application in neurorehabilitation after injury.

Action Potentials↗

PubMed2006

Correlations between the same motor cortex cells and arm muscles during a trained task, free behavior, and natural sleep in the macaque monkey.

Traditionally, the neural control of movement has been studied by recording cell activity in restrained animals performing repetitive, highly trained tasks within a restricted workspace. However, the degree to which results obtained under these conditions are valid during natural, unconstrained behavior remains unknown. Using an autonomous, implantable recording system, we examined the relationships between the firing of motor cortex cells and forearm muscle activity in primates under three behavioral conditions: performance of a conventional torque-tracking task, unrestrained behavior, and natural sleep. We found strong correlations over long periods of daytime activity, suggesting a consistent relationship between cortex and muscles across the repertoire of awake behavior. The range of correlation values was comparable during task performance, but many individual cells exhibited significant differences across conditions. During the night, phases of sleep were associated with a cyclical pattern of cell and muscle activity. Across the population, the strength of cell-muscle correlations was related to preferred direction for daytime but not nighttime activity. The relationship of cells to behavior remained consistent over periods of several weeks. These findings extend the interpretation of results obtained under constrained conditions and are relevant to the development of neural prostheses for restoring natural movements to patients with motor deficits.

Action Potentials↗

PubMed2006

The Neurochip BCI: towards a neural prosthesis for upper limb function.

The Neurochip BCI is an autonomously operating interface between an implanted computer chip and recording and stimulating electrodes in the nervous system. By converting neural activity recorded in one brain area into electrical stimuli delivered to another site, the Neurochip BCI could form the basis for a simple, direct neural prosthetic. In tests with normal, unrestrained monkeys, the Neurochip continuously recorded activity of single neurons in primary motor cortex for several weeks at a time. Cortical activity was correlated with simultaneously-recorded electromyogram (EMG) activity from arm muscles during free behavior. In separate experiments with anesthetized monkeys, we found that microstimulation of the cervical spinal cord evoked movements of the arm and hand, often involving multiple muscles synergies. These observations suggest that spinal microstimulation controlled by cortical neurons could help compensate for damaged corticospinal projections.

Animals↗

PubMed2005

An autonomous implantable computer for neural recording and stimulation in unrestrained primates.

To perform neurobiological experiments on freely behaving primates, we have developed a miniature battery-powered implantable computer capable of recording and stimulating through chronic electrodes in the cortex. The device has: (1) an analog front end with a four-pole bandpass filter (500 Hz-5 kHz), programmable gain and offset nulling; (2) an analog-to-digital converter to sample the data at 11.7 ksps; (3) a programmable microcontroller to discriminate spikes in real time and perform computations; (4) a stimulator to deliver biphasic current pulses of up to 100 muA with variable pulse width and frequency; (5) a 4 Mbit non-volatile memory to store biological data; (6) a 57.6 kbps infrared data link for wireless communications with a hand-held or desktop computer. The device is enclosed in a 5.5 cm x 5 cm x 3 cm titanium casing on the monkey's head along with a 3.3 V lithium battery and an array of cortical electrodes. In in vivo tests, the device was able to record stable cell discharge continuously for time periods of a week or more. After downloading the parameters for recording, stimulation, discrimination, and other computations, the device is capable of operating autonomously, delivering stimuli to one electrode triggered by spikes recorded at a separate site.

Action Potentials↗