Primary motor area(motor area 4)is said to be facilitatory to AHCs and hence has a facilitatory effect on muscle tone and deep reflexes.What i want to ask about is;why is a lesion in pyramidal tract (originating mainly from primary motor area) associated with hypertonia and hyperreflexia.Thank you.

I think the damage directly broadman area 4 (primary motor area) dont cause hypertony .It cause flask paralysıs but if damage to below part trough corticospinal track cause hypertony and increased reflex tone

I think it has something to do with lateral vestibular nucelus which is facilitatory and due to withdrawn inhibition of area 4 on it, it leads to hypertonia hyperreflexia.
P.S. it has been a while since I last read something about neurosciences so Im not really sure I remember the exact explanation of area4 damage leading to hyperreflexia hypertonia.

hypertonia and hyperrreflexia are the main syntohms of the Pyramidal Syndrome because the pyramidal tract is in charge of the regulation of the osteotendinose reflexes (inhibitory accion).