Table 2.

Phenotype	Description/neurobiology	Animal model	Heritability estimates	Comment
Eye tracking	Smooth pursuit of a target by the eye—involves motion processing (MT, MST), attention (posterior parietal) and predictive oculomotor (frontal eye fields) responses.	None	Depends on the measure used—recent studies with specific measures report high heritability (h2=0.7-0.9).1	Two independent studies found significant linkage of eye tracking phenotype to loci on chromosome 6p21.2,3 Association with COMT and DRD3 genes reported.4,5
P50	Sensory gating of the second of paired auditory stimuli. Modulated by nicotinic drugs, as well as adrenergic and 5HT system.	Yes-N40	Heritability estimate based on a twin study, h2=0.44.6	A finding of genetic linkage of P50 phenotype at 15q14 (near the location of α 7 nicotinic receptor gene.7,8
PPI	Sensory gating of the startle response to loud sound (pulse) by a muted auditory prepulse. Modulated by several neurotransmitter system including dopamine, glutamatergic, and 5HT.	Yes-PPI	Normal twin studies suggest that about 50% of the variance in PPI can be explained by the genetic factors.9	Early evidence suggest that the PPI phenotype is distinct from P50. QTL mapping identified loci on mouse chromosome 16.10
Sustained attention	Using a continuous performance task (CPT).	No (?)	Estimated heritability range between 0.48-0.62.11	Associated with the dopamine transporter gene in ADHD.12
Visual working memory	Neural correlates of oculomotor delayed response task are well described by human imaging and monkey neurophysiological studies.	Yes	Estimated heritability is reported to be ∼0.45 including in families of schizophrenia probands.11	Preliminary data show an association with DISC1 gene in families of schizophrenia probands.13
Verbal learning and memory	Different measures across studies tapping into this domain.	No	Estimated heritability based on healthy twin studies, h2=0.44. Similar findings in schizophrenia families, h2ranging from 0.21-0.49.11	Genome-wide data from 168 schizophrenia families suggested a locus for verbal learning and memory on 4q21.14 May be associated with BDNF gene.
Brain morphometry	Decreased total brain volume; decreased white matter volume in some tracts; and thalamic volume reductions noted in relatives of schizophrenia probands.	Yes (?)	Heritability estimates for several cortical regions are high (0.80-0.99 based on healthy twin studies).15-17	Further research with focus on specific brain morphometric measures needed.

Table 2 Courtesy of gunvant thaker, MD.