Visualizing Recovery of Cognitive Function in Stroke

Abstract

Hippocrates (460-377 BC) first described stroke over 2400 years ago. Stroke is the 4 th leading cause of death in Canada (3 rd in the USA) and the primary cause of permanent motor and cognitive disability. The majority of strokes are ischemic. The extent of cerebral dysfunction and thus the severity of stroke are based on the location, severity and duration of ischemia. Stroke management and prognosis encompass early recognition of the onset of stroke and post-stroke determination of the extent of brain injury aided by clinical stroke scores and diffusion-weighted imaging. Cognitive domains most likely to be affected following stroke are memory, orientation, language, attention and executive function. While the vast majority of functional recovery occurs within the first 3 months post-stroke, the neural mechanisms promoting recovery are not well understood. Investigations into the neural plasticity of brain areas after a lesion demonstrate that the adult brain can be shaped by environmental inputs, such as rehabilitation techniques. Many rehabilitation techniques are actively being pursued, including brain-computer interfaces providing sophisticated methods for detecting rehabilitation-associated changes in cerebral physiology. The success of such strategies visualized with functional magnetic resonance imaging and positron emission tomography may provide an objective complement to clinical evaluations.

Effects and mechanism of the HECT study (hybrid exercise-cognitive trainings) in mild ischemic stroke with cognitive decline: fMRI for brain plasticity, biomarker and behavioral analysis

“…Although resting-state fMRI can elucidate the brain's functional connections by determining temporal synchrony between brain regions, whether the training-induced changes in the neural activity associated with cognitive training remains unexplored. Event-related fMRI with BOLD contrast technique might be better in representing functionality of brain regions at least in normal subjects performing various cognitive tasks [ 59 ]. To the best of our knowledge, only one case study investigated the patterns of neural activation after a course of auditory working memory training using event-related fMRI.…”

Stroke in Frail Older People

“…Many older people will not have a “normal” brain [21]; for many, a routine Computed Tomograph (CT) brain scan either before or after stroke reveals diffuse periventricular ischaemia [22]. These are associated with dementia, infection, Parkinsonism, motor disorders and stroke recurrence.…”

“…Stroke recovery requires neuroplasticity to occur, however animal studies have suggested that with increasing age there is a reduction in neurogenesis in basal hippocampus regions compared to striatal-like regions [63]. The presence of an ischaemic brain [22] pre-stroke status will affect post-stroke recovery; particularly executive functioning and memory task processing will be affected [22]. The presence of a high load of periventricular ischaemia would suggest a reduction in brain reserve, and hence the ability to rewire the brain [64,65] may be reduced [66].…”