No abstract

Motor imagery, the 'mental rehearsal of motor acts without overt movements', involves either a visual representation (visual imagery, VI) or mental simulation of movement, associated with a kinesthetic feeling (kinetic imagery, KI). Previous brain imaging work suggests that patterns of brain activation differ when comparing execution (E) with either type of imagery but the functional connectivity of the participating networks has not been studied. Using functional magnetic resonance imaging (fMRI) and structural equation modeling, this study elucidates the inter-relationships among the relevant areas for each of the three motor behaviors. Our results suggest that networks underlying these behaviors are not identical, despite the extensive overlap between E and KI. Inputs to M1, which are facilitatory during E, have the opposite effect during KI, suggesting a physiological mechanism whereby the system prevents overt movements. Finally, this study highlights the role of the connection of superior parietal lobule to the supplementary motor area in both types of motor imagery.

Maternal sensory signals in early life play a crucial role in programming the structure and function of the developing brain, promoting vulnerability or resilience to emotional and cognitive disorders. In rodent models of early-life stress, fragmentation and unpredictability of maternally derived sensory signals provoke persistent cognitive and emotional dysfunction in offspring. Similar variability and inconsistency of maternal signals during both gestation and early postnatal human life may influence development of emotional and cognitive functions, including those that underlie later depression and anxiety.

REVENTION IS A GOAL TO WHICH every field of medicine aspires because it reduces morbidity, may alleviate suffering, and reduces the cost of health care. Although the Commission on Chronic Illness proposed the classification of primary, secondary, and tertiary prevention 1 in 1957, the Institute of Medicine Committee on Prevention of Mental Disorders recommended a new terminology 2 in 1995. According to the new terminology, preventive intervention is defined as an intervention before the patient receives a diagnosis. Alternatively, treatment is an intervention for patients already with a diagnosis, and maintenance is the care of patients with chronic illnesses including relapse prevention. Furthermore, preventive interventions are categorized as (1) indicated, addressing high-risk individuals with premorbid signs or symptoms; (2) selective, for select individuals with demonstrated increased risk of developing illness; and (3) universal, for a whole population in a group with all levels of risk. Although the ultimate goal of preventive intervention in mental disorders is universal, the major problem is See also Patient Page.

No abstract

An experimental lesion in the primary motor or sensory cortices in monkeys leads to functional reorganization in areas surrounding the lesion or in contralateral homologous regions. In humans, task-dependent brain activation after motor stroke seems to be multifocal and bilateral. Although many active structures are seen after stroke, their roles are unclear. For instance, the uninjured primary motor cortex may play a significant role in recovery or may be associated with mirror movements. Other motor areas, particularly those outside the affected middle cerebral artery distribution, have also been thought to play such a role, including the medial pre-motor areas and both cerebellar hemispheres. The lateral pre-motor areas might also contribute but the demarcation of primary motor and pre-motor cortices is not trivial. It is not known from existing studies how brain activation relates to behavioural change over the time course of recovery. We used functional MRI (fMRI) to study 12 patients longitudinally over the first 6 months of stroke recovery. All subjects had acute stroke causing unilateral arm weakness and had some ability to move the impaired hand within 1 month. Each patient had both motor testing and fMRI during finger and wrist movements at four points during the observed period. Six of these patients showed good motor recovery, whereas the other six did not. The imaging results support a role for the cerebellum in mediating functional recovery from stroke. The data suggest that patients with good recovery have clear changes in the activation of the cerebellar hemisphere opposite the injured corticospinal tract. Patients with poor recovery do not show such changes in cerebellar activation. No other brain region had a significant correlation with recovery. Interestingly, activation in the cerebellum ipsilateral to the injury increases transiently after stroke, independently of the success of recovery. The present work suggests a possible link between cerebellar activation and behavioural recovery from hand weakness from stroke. The underlying mechanism is not known, but it could relate to haemodynamic changes such as diaschisis or to the postulated role of the cerebellum in motor skill learning.

No abstract

Although functional lateralization in the human brain has been studied intensively, there remains significant controversy over the brain mechanisms that instantiate it. The main objective of the present study is to characterize the regions associated with the generation of different movements by the fingers of both hands by right- and left-handed people. Thirteen right- and left-handers were studied using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) during performance of single and sequential finger movement tasks. We used single-shot whole-brain spiral fMRI to map the functional components of the motor system during these tasks. Regions of interest included the primary motor and sensory cortices, the pre-motor cortices and the cerebellum. Sequential movements were associated with intense brain activation in several bilateral regions, whereas single movements were associated with less activation in fewer regions, but with greater laterality. Right- and left-handers differed in their pattern of activation, sharing a pattern of activation on simple movements but responding differently to sequential movements. On simple movements, the brain activation patterns of left- and right-handers were similar in volume, number of areas and laterality. By contrast, on sequential movement, left-handers activated larger volumes and a larger number of brain areas than right-handers, and showed significantly less brain lateralization. These results highlight differences in the functional organization of motor areas in right- and left-handed people. The discrepancies that might reflect differences in the network features of motor systems in these two groups, could also determine differences in motor activity that occur during recovery from injury (e.g. after stroke).