For decades, neurologists have used two-point discrimination(2PD) as a tool for diagnosing neurological dysfunction. 2PD involves stimulating a patient with the tips of a caliper and asking:"were you touched with two points or one?" As the separation be-tween tips decreases to zero, so too should the patient's probability of responding "two-points"; the reasoning for this is that two pointsthat fall between adjacent touch receptors should not be reliably dis-tinguishable from a single point between these same receptors. Re-markably, many patients are able to reliably distinguish two pointsfrom one, even when the two points have zero separation (Johnson &Phillips, 1981). This "hyper acuity" might be explained by the fact thata single receptor neuron fires a greater number of impulses to a sin-gle indentation than to a double indentation of the same depth (Vega-Bermudez & Johnson, 1999), thus leading to a magnitude differencethat the brain can use to discriminate two points at extremely smallspacing. We have designed a new clinical screening test that avoidsthis "magnitude-cue" confound: by having patients identify the orienta-tion of two-point stimuli (horizontal or vertical) in a two-point orienta-tion discrimination (2POD) task, patients must rely on purely spatialinformation to discern orientation. As expected for a true measure ofspatial acuity, 2POD performance approaches chance levels at zeroseparation, unlike the 2PD task. We recommend replacing the 2PD task with 2POD in clinical settings.
CITATION: Tong J, Mao O, Goldreich D (2013) Front Hum Neurosci 7:579.
AREA: Sensory Systems
Functional imaging studies in schizophrenic patients have demonstrated metabolic brain abnormalities during cognitive tasks.This study aimed to 1) introduce a novel analysis of brain metabolicfunction in live animals to characterize the hypo- and hyperfrontalityphenomena observed in schizophrenia and following NMDA antago-nist exposure, and 2) identify a robust and representative MK-801treatment regimen that effectively models brain metabolic abnormali-ties as well as a range of established behavioural abnormalities repre-sentative of schizophrenia. Acute treatment at 0.5 mg/kg-disruptedfacets of memory measured through performance in the 8-arm radialmaze task and generated abnormalities in sensorimotor gating, socialinteraction and locomotor activity. Furthermore, this treatment regi-men induced hyperfrontality (increased brain metabolic function in the prefrontal area) observed via PET/CT fused imaging in the live rat. These findings provide insight on the effectiveness of the MK-801pre-clinical model of schizophrenia and provide an optimal regimen to model schizophrenia. PET/CT fused imaging offers a highly translateable tool to assess hypo- and hyperfrontality in live animals.
CITATION: Daya RP, Bhandari JK, Hui PA, Tian Y, Farncombe T,Mishra RK (2014) Neuropharmacol 77: 325–333.
AREA: Neuropsychiatric Disease