Neuroscience
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Prior adverse experience alters behavioral responses to subsequent stressors. For example, exposure to a brief swim increases immobility in a subsequent swim test 24h later. In order to determine if qualitative differences (e.g. 19°C versus 25°C) in an initial stressor (15-min swim) impact behavioral, physiological, and associated neural responses in a 5-min, 25°C swim test 24h later, rats were surgically implanted with biotelemetry devices 1 week prior to experimentation then randomly assigned to one of six conditions (Day 1 (15 min)/Day 2 (5 min)): (1) home cage (HC)/HC, (2) HC/25°C swim, (3) 19°C swim/HC, (4) 19°C swim/25°C swim, (5) 25°C swim/HC, (6) 25°C swim/25°C swim. ⋯ The 19°C swim on Day 1, relative to HC exposure on Day 1, increased immobility during the 5-min swim on Day 2. Also, 19°C swim, relative to HC conditions, on Day 1 reduced swim (25°C)-induced increases in c-Fos expression in serotonergic neurons within the dorsal and interfascicular parts of the dorsal raphe nucleus. These results suggest that exposure to a 5-min 19°C cold water swim, but not exposure to a 5-min 25°C swim alters physiological, behavioral and serotonergic responses to a subsequent stressor.
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The neuropeptide oxytocin (OT) regulates rodent, primate and human social behaviors and stress responses. OT binding studies employing (125)I-d(CH2)5-[Tyr(Me)2,Thr4,Tyr-NH2(9)] ornithine vasotocin ((125)I-OTA), has been used to locate and quantify OT receptors (OTRs) in numerous areas of the rat brain. This ligand has also been applied to locating OTRs in the human brain. ⋯ OTR staining was not observed in the hippocampus (including CA2 and CA3), parietal cortex, raphe nucleus, nucleus ambiguus or pons. These results suggest that there are some similarities, but also important differences, in the locations of OTRs in human and rodent brains. Immunohistochemistry (IHC) utilizing a monoclonal antibody provides specific localization of OTRs in the human brain and thereby provides opportunity to further study OTR in human development and psychiatric conditions.
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Speech comprehension relies on auditory as well as visual information, and is enhanced in healthy subjects, when audiovisual (AV) information is present. Patients with schizophrenia have been reported to have problems regarding this AV integration process, but little is known about which underlying neural processes are altered. Functional magnetic resonance imaging was performed in 15 schizophrenia patients (SP) and 15 healthy controls (HC) to study functional connectivity of Broca's area by means of a beta series correlation method during perception of audiovisually presented bisyllabic German nouns, in which audio and video either matched or did not match. ⋯ These smaller differences in connectivity in SP suggest a less adaptive processing of audiovisually congruent and incongruent speech. The findings imply that AV integration problems in schizophrenia are associated with maladaptive connectivity of Broca's and RpSTS area in particular when confronted with incongruent stimuli. Results are discussed in light of recent AV speech perception models.
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The auditory system continuously monitors the environment for irregularities in an automatic, preattentive fashion. This is presumably accomplished by two mechanisms: a sensory mechanism detects a deviant sound on the basis of differential refractoriness of neural populations sensitive to the standard and deviant sounds, whereas the cognitive mechanism reveals deviance by comparing incoming auditory information with a template derived from previous input. ⋯ The sensory mechanism is supported by primary auditory areas in Heschl's gyrus whereas the cognitive mechanism is implemented in more anterior secondary auditory areas. Both mechanisms are equally engaged by simple sine-wave tones and speech-related phonemes indicating that streams of speech and non-speech stimuli are processed in a similar fashion.
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Noradrenaline (NA) in the hippocampus plays an important role in memory function and has been shown to modulate different forms of synaptic plasticity. Oscillations in the gamma frequency (20-80 Hz) band in the hippocampus have also been proposed to play an important role in memory functions and, evidence from both in vitro and in vivo studies, has suggested this activity can be modulated by NA. However, the role of different NA receptor subtypes in the modulation of gamma frequency activity has not been fully elucidated. ⋯ Using specific agonists and antagonists of AR receptor subtypes we demonstrated that these effects are mediated specifically via α1A-AR and β1-AR subtypes. NA activated both receptor subtypes, but the α1A-AR-mediated effect predominated, resulting in a reversible suppression of gamma frequency activity. These results suggest that NA is able to differentially modulate on-going gamma frequency oscillatory activity that could result in either increased or decreased information flow through the hippocampus.