Cortical oscillatory dysfunction in Parkinson disease during movement activation and inhibition

Response activation and inhibition are functions fundamental to executive control that are disrupted in Parkinson disease (PD). We used magnetoencephalography to examine event related changes in oscillatory power amplitude, peak latency and frequency in cortical networks subserving these functions and identified abnormalities associated with PD. Participants (N = 18 PD, 18 control) performed a cue/target task that required initiation of an un-cued movement (activation) or inhibition of a cued movement. Reaction times were variable but similar across groups. Task related responses in gamma, alpha, and beta power were found across cortical networks including motor cortex, supplementary and pre- supplementary motor cortex, posterior parietal cortex, prefrontal cortex and anterior cingulate. PD-related changes in power and latency were noted most frequently in the beta band, however, abnormal power and delayed peak latency in the alpha band in the pre-supplementary motor area was suggestive of a compensatory mechanism. PD peak power was delayed in pre-supplementary motor area, motor cortex, and medial frontal gyrus only for activation, which is consistent with deficits in un-cued (as opposed to cued) movement initiation characteristic of PD.

Resting state functional connectivity is associated with cognitive dysfunction in non-demented people with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) can result in cognitive impairment. Executive dysfunction often appears early, followed by more widespread deficits later in the course of the disease. Disruption of parallel basal ganglia thalamo-cortical loops that subserve motor and cognitive function has been described in PD. However, there is emerging evidence that the default mode network, a cortical network that is active at rest with reduced activation during task performance, may also play a role in disease related cognitive decline.

OBJECTIVE

To determine the relative contribution of the executive control and default mode networks to parkinsonian executive dysfunction in medicated non-demented patients.

METHODS

We used BOLD fMRI to measure resting state functional connectivity in the executive control and default mode (DM) networks, and examined switching, processing speed, working memory/attention and motor performance in 14 medicated non-demented PD participants and 20 controls.

RESULTS

Performance on neuropsychological measures was similar across groups. Functional connectivity was not different across disease conditions in the executive control network. DMN functional connectivity was decreased in the PD group, specifically between posterior cingulate, medial prefrontal, and inferior parietal nodes. Greater DMN functional connectivity was associated with faster processing speed in the PD group.

CONCLUSIONS

The continuous relationship between DMN disconnection and executive task performance indicates a possible biological contributor to parkinsonian cognitive deficits. The dynamics of executive control network change may be different than that of the DMN, suggesting less sensitivity to early cognitive deficits.

Perceived and performance-based executive dysfunction in Parkinson's disease

Executive dysfunction is common in early stage Parkinson's disease (PD). We evaluated the relationship between self- and informant-report measurement of real-world executive functions as well as performance-based neuropsychological measures in mildly cognitively impaired individuals with PD and healthy controls. The PD group reported more difficulty with initiation of complex tasks compared to caregiver ratings, and processing speed was a strong predictor of self-reported executive dysfunction for the PD group, followed by depression. Processing speed and semantic verbal fluency predicted informant-reported executive dysfunction in PD. These findings highlight the contribution of speeded processing for performance of everyday executive tasks in PD.