Forelimb Whiskers Forelimb area Whisker area Lateral Inhibitory local circuit ne
ID: 3477690 • Letter: F
Question
Forelimb Whiskers Forelimb area Whisker area Lateral Inhibitory local circuit neuron 3.5 2.5 1.5 Medal o5 2.5 Coordinate Imm) 4.5 0.5 Anterior Posterior Somatotopic arrangement after transection of facial nerve Lateral 4.5 2.5 Meda 0.5 2.5 Coordinate Imm) 4.5 0.5 1.5 Figure 37-17 The functional organization of the motor map inhibitory circuits in the motor cortex. Under normal condi- of a rat changes rapidly after transection of the facial nerve. tons (topl the excitatory effect of horizontal axonal projections Reproduced, with permission, from Sanes et al. 1988 and from bween different parts of the motor map is subject to inhibi Jacobs and Doncghue 1991.) A. A surface view of the rat's frontal cortex shows the normal somatotopic arrangement of areas representing forelimb, whisker, and periocular muscles. Within minutes after transec- tion of the branches of the facial nerve that innervate whiskers, stimulation of cortical sites that f muscles causes contraction of forelimb and periocular muscles. periocular sites through horizontal axonal collaterals whose B. Elimination of the sensory inputs after transection of the facial nerve may lead to rapid changes in the balance of local tion mediated by local inhibitory interneurons, so that electri- cal stimulation of a whisker site evokes contractions of only whisker muscles and not forelimb muscles. lontophoretic injec- tion of bicuculline into a forelimb site in the motor map blocks local GABA-mediated inhibition (bottom). As a result, stimula- tion of whisker sites can excite output neurons in forelimb and ormerly a influence is normally restricted by inhibitory interneurons.Explanation / Answer
(1) What specifically was done to test for rearrangements of the motor map
Answer: Functional- MRI and voltage-sensitive dye (VSD) imaging are done to study rearrangements of the motor map
(2) How these procedures impacted the motor map
Answers: The whiskers area in motor cortex is abolished and this area has been occupied by forelimb and periocular areas.
(3) The neuronal circuit hypothesized to underlie these rearrangements
This may be due to plasticity of central nervous system neuronal areas.
These areas change according to use or disuse of that particular part of the body or the performance of that particular movement, over a period of time.