Somatosensory gating and recovery from stroke involving the thalamus.
OBJECTIVE
In the undamaged brain, sensory input to the cortex is intricately controlled via sensory gating mechanisms. Given the role of corticothalamic pathways in this control, it was hypothesized that in patients recovering from thalamic stroke there would be evidence of disrupted sensory gating and that efficient control of cortical sensory inputs would emerge during recovery.


METHODS
Four patients were tested serially after stroke from 1 to 24 weeks after injury. Perceptual thresholds, somatosensory evoked potential amplitudes, and functional MRI activations under specific somatosensory stimulation conditions were measured.


RESULTS
All patients demonstrated comparable results, revealing disrupted threshold detection to vibrotactile stimuli in the presence of a concurrent competing, contralateral input. In contrast, threshold detection was comparable between the affected and unaffected sides when there were no competing stimuli. This compromised capacity to inhibit competing sensory inputs was paralleled by a reduction in the measured activation of cortical representation in the stroke-affected hemisphere (functional MRI and somatosensory evoked potential) during bilateral stimulation. After recovery, perceptual detection improvements during bilateral stimulation were paralleled by enhancements of primary somatosensory cortical activation in the stroke-affected hemisphere.


CONCLUSIONS
These results provide insight into potential mechanisms that contribute to sensory gating and suggest that the ability to control sensory input through effective gating mechanisms, in addition to primary somatosensory representation, may be important for poststroke sensory recovery.
Staines
W Richard
WR
Department of Kinesiology and Health Science, York University, Toronto, Ontario, Canada. rstaines@yorku.ca
Black
Sandra E
SE
Graham
Simon J
SJ
McIlroy
William E
WE
D000368:Aged; D005073:Evoked Potentials, Somatosensory; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010812:Physical Stimulation / Q000379:methods; D020127:Recovery of Function; D012684:Sensory Thresholds; D020521:Stroke / Q000175:diagnosis* / Q000503:physiopathology*; D000071939:Stroke Rehabilitation; D013788:Thalamus / Q000098:blood supply / Q000503:physiopathology*; D014732:Vibration