State-dependent spike and local field synchronization between motor cortex and substantia nigra in hemiparkinsonian rats.
Excessive beta frequency oscillatory and synchronized activity has been reported in the basal ganglia of parkinsonian patients and animal models of the disease. To gain insight into processes underlying this activity, this study explores relationships between oscillatory activity in motor cortex and basal ganglia output in behaving rats after dopamine cell lesion. During inattentive rest, 7 d after lesion, increases in motor cortex-substantia nigra pars reticulata (SNpr) coherence emerged in the 8-25 Hz range, with significant increases in local field potential (LFP) power in SNpr but not motor cortex. In contrast, during treadmill walking, marked increases in both motor cortex and SNpr LFP power, as well as coherence, emerged in the 25-40 Hz band with a peak frequency at 30-35 Hz. Spike-triggered waveform averages showed that 77% of SNpr neurons, 77% of putative cortical interneurons, and 44% of putative pyramidal neurons were significantly phase-locked to the increased cortical LFP activity in the 25-40 Hz range. Although the mean lag between cortical and SNpr LFPs fluctuated around zero, SNpr neurons phase-locked to cortical LFP oscillations fired, on average, 17 ms after synchronized spiking in motor cortex. High coherence between LFP oscillations in cortex and SNpr supports the view that cortical activity facilitates entrainment and synchronization of activity in basal ganglia after loss of dopamine. However, the dramatic increases in cortical power and relative timing of phase-locked spiking in these areas suggest that additional processes help shape the frequency-specific tuning of the basal ganglia-thalamocortical network during ongoing motor activity.
Neurophysiological Pharmacology Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892-3702, USA.
Elena
E
Brazhnik
Ana V
AV
Cruz
Irene
I
Avila
Marian I
MI
Wahba
Nikolay
N
Novikov
Neda M
NM
Ilieva
Alex J
AJ
McCoy
Colin
C
Gerber
Judith R
JR
Walters
D000818:Animals; D000978:Antiparkinson Agents / Q000494:pharmacology; D003344:Cortical Synchronization; D003627:Data Interpretation, Statistical; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004576:Electromyography; D007980:Levodopa / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009043:Motor Activity / Q000502:physiology; D009044:Motor Cortex / Q000187:drug effects / Q000502:physiology*; D010302:Parkinson Disease, Secondary / Q000503:physiopathology*; D051381:Rats; D020318:Rats, Long-Evans; D012146:Rest / Q000502:physiology; D013378:Substantia Nigra / Q000187:drug effects / Q000502:physiology*; D016138:Walking / Q000502:physiology
D000978:Antiparkinson Agents; D018492:Dopamine Antagonists; D007980:Levodopa; D004298:Dopamine