Different Functional Loops between Cerebral Cortex and the Subthalmic Area in Parkinson's Disease

Abstract

We investigate the extent to which functional circuits coupling cortical and subthalamic activity are multiple and segregated by frequency in untreated Parkinson's disease (PD). To this end, we recorded EEG and local field potentials (LFPs) from macroelectrodes inserted into the subthalamic nucleus area (SA) in nine awake patients following functional neurosurgery for PD. Patients were studied after overnight withdrawal of medication. Coherence between EEG and SA LFPs was apparent in the theta (3-7 Hz), alpha (8-13 Hz), lower beta (14-20 Hz) and upper beta (21-32 Hz) bands, although activity in the alpha and upper beta bands dominated. Theta coherence predominantly involved mesial and lateral areas, alpha and lower beta coherence the mesial and ipsilateral motor areas, and upper beta coherence the midline cortex. SA LFPs led EEG in the theta band. In contrast, EEG led the depth LFP in the lower and upper beta bands. SA LFP activity in the alpha band could either lead or lag EEG. Thus there are several functional sub-loops between the subthalamic area and cerebral cortical motor regions, distinguished by their frequency, cortical topography and temporal relationships. Tuning to distinct frequencies may provide a means of marking and segregating related processing, over and above any anatomical segregation of processing streams.

High Thalamocortical Theta Coherence in Patients with Parkinson's Disease

“…The magnitude of ␤ coherence, however, was below 16% and thereby much lower than in the theta band. Values of similar magnitude were reported for ␤ coherence between scalp EEG and recording sites in the cerebellar thalamus (Marsden et al, 2000;Paradiso et al, 2004) and basal ganglia (Marsden et al, 2001;Williams et al, 2002;Fogelson et al, 2006), indicating that activity at these sites also interacts with cortical activity. Anatomically and functionally, the main output of the basal ganglia occurs via the pallidothalamic and nigrothalamic tract to the thalamus.…”

“…LFP recordings come mainly from sites in the cerebellar thalamus (Marsden et al, 2000;Paradiso et al, 2004) or in the basal ganglia (Marsden et al, 2001;Williams et al, 2002;Fogelson et al, 2006) and reflect the sites of surgical intervention.…”

Wavelet Energy and Wavelet Coherence as EEG Biomarkers for the Diagnosis of Parkinson’s Disease-Related Dementia and Alzheimer’s Disease

“…Because higher WC was found in temporo-parietal channel pairs in the PD-D group, this abnormal synchrony might result from impairment of the sensorimotor cortex. Abnormal synchrony might cause motor symptoms such as tremors [36,49]. Several studies have reported that high WC might result from synchrony of thalamo-cortical oscillatory activity due to the deterioration of the substantia nigra in PD patients [45,46].…”

Beta Reactivity, Prospective Facilitation of Executive Processing, and Its Dependence on Dopaminergic Therapy in Parkinson's Disease

“…Of particular note, reduction in the power of cortical beta-band activity during motor preparation scales with the directional uncertainty of forthcoming movement, and this in turn correlates with the change of latency with response uncertainty (Tzagarakis et al, 2010). Other limitations are the presumptive localization of electrode contacts in the STN (Williams et al, 2002;Fogelson et al, 2006) and the possibility that power changes picked up at the bipolar contacts of the DBS electrode are not really focally generated. Against the latter, we found a steep gradient in LFP power in the beta band across different bipolar contact pairs consistent with a local generator (Kühn et al, 2004(Kühn et al, , 2006, although the strongest argument in favor of the local generation of beta activity in the LFP is the demonstration that the discharge of neurons in the STN tends to be locked to it (Levy et al, 2002;Kühn et al, 2005).…”