Premium
P3‐244: Elevated Physiological Fluctuations in White Matter is Related to Disease Severity in Patients with Parkinson's Disease
Author(s) -
Shirzadi Zahra,
Sharmarke Hanad,
Robertson Andrew D.,
Metcalfe Arron W.S.,
Duff-Canning Sarah,
Marras Connie,
Lang Anthony E.,
Masellis Mario,
MacIntosh Bradley J.
Publication year - 2016
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2016.06.1906
Subject(s) - white matter , grey matter , cognition , psychology , neuroimaging , parkinson's disease , effects of sleep deprivation on cognitive performance , physical medicine and rehabilitation , atrophy , disease , alzheimer's disease neuroimaging initiative , multivariate statistics , audiology , medicine , cardiology , neuroscience , magnetic resonance imaging , cognitive impairment , statistics , mathematics , radiology
Background:Contextual orientation (CO) is often utilized in assessments such as MMSE and MoCA commonly employed in AD and dementia care. Tests often assess CO through probes of mental orientation (e.g. What month is it?). The loss of orientation in time, space and person in dementia patients may contribute to the difficulties observed for episodic memory, theory of mind, and spatial navigation tasks in these patients. While commonly utilized in longstanding behaviour-based assessments, the neuronal mechanisms of CO are not well characterized, and an electrophysiological indicator of CO has not been identified. Methods: An auditory stimulus sequence consisting of a stream of 100 words was created (40 words with CO salience/relevance, 60 without; groups balanced for word frequency and length). Examples of CO-salient words include current day of the week, season, month, and location. 151-channel MEG and concurrent electroencephalography (EEG) data were collected on 15 healthy individuals (age 18-40) with simultaneous auditory stimulation. For sensor level analysis, MEG and EEG data were filtered (1-10Hz), segmented (CO relevant vs. irrelevant) and conditionally averaged. Global field power (GFP) measurements were conducted for each of two conditions separately, and non-parametric statistics were employed to identify statistically significant differences between conditions. Source level analyses were undertaken using Minimum Norm technique in Statistical Parametric Mapping (SPM8) software. Results:GFP results indicate significant differences between the CO relevant and irrelevant conditions in the 353-573ms window in MEG, whereas EEG data demonstrated a significant difference in the 227-383ms window (p<0.05). Analysis of the conditionally averaged EEG data demonstrated a larger positive deflection for the CO relevant condition relative to the irrelevant condition (p<0.05). The timing and spatial distribution of this positivity indicates a P300-like response to the CO relevant stimuli. Conclusions: To our knowledge, this is the first passive auditory paradigm that elicits CO related neural responses. Initial results demonstrate significant differences in brain activations between the CO relevant and irrelevant conditions, enabling the identification of a P300-like indicator for CO. This technique can potentially be utilized in bedside assessments in dementia and other neurological disorders characterized by disruptions in mental orientation.