ABSTRACT
Prepulse inhibition (PPI) is suppression of the startle reflex when an intense startling stimulus is preceded by a weaker sensory stimulus (the prepulse). It is an operational measurement of sensorimotor gating mechanism to help human adapt to complex environment. This weak prepulse protect central cognitive processing by damping the effect of intense stimuli. Autistics cannot select out behaviorally important information from a lot of irrelevant resources and reflect abnormal gating mechanism and attentional abnormalities. Previous studies have not made agreement on whether autistic patients demonstrated deficits in PPI, because the results depend on age, sex, severity of the disease as well as the experimental parameters used. Moreover, these studies have not covered whether autistics have suffered deficits in higher-order processing. In this review, the "top-down" modulation of selective attention and subjective emotion are introduced into the PPI experiment. We also introduce fear conditioning and perceived spatial separation paradigm to further explore the interaction between autistic cognitive process and gating mechanism.
Subject(s)
Humans , Attention , Autistic Disorder , Fear , Prepulse Inhibition , Reflex, StartleABSTRACT
Social isolation influences the development of the brain, causing dysfunctions at behavioral, cellular and molecular levels. The present paper summarizes the abnormalities induced by social isolation in behaviors, neurotransmitters and cell apoptosis. At the behavioral level, social isolation induces hyperlocomotion, abnormalities in startle reflex and prepulse inhibition (PPI), and dysfunctions in conditioned learning, reversal learning and memory. Moreover, social isolation causes changes of neurotransmitters, such as the increase of dopamine in the nucleus accumbens, the amygdala and other brain regions in the limbic system, the decrease of dopamine in medial prefrontal cortex, the decrease of 5-HT in the nucleus accumbens and the hippocampus, and changes of glutamine in the prefrontal cortex. Finally, social isolation affects cell apoptosis in different brain areas, such as the medial prefrontal cortex, amygdala, nucleus accumbens, and hippocampus. Both the changes in neurotransmitters and cell apoptosis may contribute to the behavioral dysfunctions in social isolated rats. Since schizophrenic patients have similar abnormalities in behaviors and neurotransmitters, isolation rearing can be used as a useful animal model of schizophrenia.
Subject(s)
Animals , Rats , Brain , Disease Models, Animal , Neurotransmitter Agents , Metabolism , Schizophrenia , Social IsolationABSTRACT
Similar to the visual dual-pathway model, neurophysiological studies in non-human primates have suggested that the dual-pathway model is also applicable for explaining auditory cortical processing, including the ventral "what" pathway for object identification and the dorsal "where" pathway for spatial localization. This review summarizes evidence from human neuroimaging studies supporting the dual-pathway model for auditory cortical processing in humans.
