Table 2.

TMS biomarkers in neurodevelopmental disorders.

Disorder	MT	MEP amplitude	cSP	I/O curve slope	SICI	ICF	LICI	TBS	PAS	Clinical correlates	Comments
Autism spectrum disorder	–	–	–		↓, –	↓, –	–	↑ cTBS/iTBS duration in adults and children; ⊥cTBS-induced facilitation in children	↓	greater SICI and prolonged cSP negatively correlated w/ academic performance; ICF inversely correlated w/ inattention and executive dysfunction reduced SICI correlated w/ developmental delay in language acquisition	positive correlation between age and cTBS-induced modulation or maximum cTBS-induced inhibition
Fragile X syndrome					–		–	↓ cTBS response; ↑ iTBS response; ↓ cTBS duration; ⊥cTBS-induced facilitation on 2nd visit			complete blocking of iTBS response on 2nd visit normal SICI and LICI could be due to unaffected X chromosome / non-optimal ISI
Attention-deficit hyperactivity disorder	↑, –		–, ↓		↓, ⊥ SICI-induced facilitation in a few cases	↓, ↑, –	↓			SICI inversely correlated w/ symptom severity ISP duration correlated w/ hyperactivity and restlessness SICI index of response to MPH	SICI inversely correlated w/ ISP duration ↑ iSP latency in children ↑ iSP duration in children ↓ iSP latency in adults ICF greater in ASD children w/ ADHD than in ASD children w/o ADHD
Tourette syndrome	–, ↑	↓ during movement preparation and volunatry tic inhibition	↓, –	↓, –	↓	↑, –		↑, ↓ iTBS response ↓ cTBS response	⊥ PAS-induced inhibition	reduced SICI positively correlated w/ motor tic severity SICI normalization during movement preparation correlated w/ fewer tics and lower tic severity PAS-induced inhibition correlated with less severe urges and fewer tics	↑ MEP variability ↓ I/O curve slope during voluntary tic inhibition
Developmental stuttering	↑		↑ for tongue	↓ for hand; ↑ for tongue	↓ for tongue	↓ for tongue				cSP duration negatively correlated w/ stuttering severity in males extent of higher aMT for tongue in left M1 relative to right M1 correlated with stuttering severity	aMT for tongue in left M1 higher than in right M1

ADHD, attention-deficit hyperactivity disorder; aMT, active motor threshold; ASD, autism spectrum disorder; cSP, cortical silent period; cTBS, continuous theta-burst stimulation; ICF, intracortical facilitation; I/O, input/output; ISI, inter-stimulus interval; iSP, ipsilateral silent period; iTBS, intermittent theta-burst stimulation; LICI, long-interval intracortical inhibition; M1, primary motor cortex; MEP, motor evoked potential; MPH, methylphenidate; MT, motor threshold; nTMS, neuronavigated transcranial magnetic stimulation; PAS, paired associative stimulation; SICF, short-interval intracortical facilitation; SICI, short-interval intracortical inhibition; TBS, theta-burst stimulation; w/, with; w/o, without; ↑ increase; ↓ decrease; – no change; ⊥ paradoxical; blank cells, not tested;, conflicting results.