Hippocampal involvement in detection of deviant auditory and visual stimuli
Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305-5719, USA. Hippocampus
(Impact Factor: 4.16).
01/2005; 15(1):132-9. DOI: 10.1002/hipo.20039
Recent models of hippocampal function have emphasized its role in processing sequences of events. In this study, we used an oddball task to investigate hippocampal responses to the detection of deviant "target" stimuli that were embedded in a sequence of repetitive "standard" stimuli. Evidence from intracranial event-related potential studies has suggested a critical role for the hippocampus in oddball tasks. However, functional neuroimaging experiments have failed to detect activation in the hippocampus in response to deviant stimuli. Our study aimed to resolve this discrepancy by using a novel functional magnetic resonance imaging (fMRI) technique that drastically improves signal detection in the hippocampus. Significant hippocampal activation was observed during both auditory and visual oddball tasks. Although there was no difference in the overall level of hippocampal activation in the two modalities, significant modality differences in the profile of activation along the long axis of the hippocampus were observed. In both left and right hippocampi, an anterior-to-posterior gradient in the activation (anterior to posterior) was observed during the auditory oddball task, whereas a posterior-to-anterior gradient (posterior to anterior) was observed during the visual oddball task. These results indicate that the hippocampus is involved in the detection of deviant stimuli regardless of stimulus modality, and that there are prominent modality differences along the long axis of the hippocampus. The implications of our findings for understanding hippocampal involvement in processing sequences of events are discussed.
Available from: link.springer.com
- "Our results might therefore indicate that the subjects with PTSD needed to give greater attention to the task in order to achieve normal results. Both auditory and visual stimulus processing in working memory are associated with hippocampal activation , and the hippocampus is involved in the processing mechanisms that determine attentional allocation and P300 amplitude . A large asymmetry of hippocampal structures may necessitate a change in the neurophysiology of non-traumatic stimulus encoding, reflected in the enlarged P300 components. "
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PTSD is associated with reduction in hippocampal volume and abnormalities in hippocampal function. Hippocampal asymmetry has received less attention, but potentially could indicate lateralised differences in vulnerability to trauma. The P300 event-related potential component reflects the immediate processing of significant environmental stimuli and has generators in several brain regions including the hippocampus. P300 amplitude is generally reduced in people with PTSD.
Our study examined hippocampal volume asymmetry and the relationship between hippocampal asymmetry and P300 amplitude in male monozygotic twins discordant for Vietnam combat exposure. Lateralised hippocampal volume and P300 data were obtained from 70 male participants, of whom 12 had PTSD. We were able to compare (1) combat veterans with current PTSD; (2) their non-combat-exposed co-twins; (3) combat veterans without current PTSD and (4) their non-combat-exposed co-twins.
There were no significant differences between groups in hippocampal asymmetry. There were no group differences in performance of an auditory oddball target detection task or in P300 amplitude. There was a significant positive correlation between P300 amplitude and the magnitude of hippocampal asymmetry in participants with PTSD.
These findings suggest that greater hippocampal asymmetry in PTSD is associated with a need to allocate more attentional resources when processing significant environmental stimuli.
Biology of Mood and Anxiety Disorders 12/2012; 2(1):21. DOI:10.1186/2045-5380-2-21
Available from: Vince Calhoun
- "This functional trend may help explain the neural mechanisms associated with the behavioral results. The anterior cingulate and hippocampus, which are commonly linked to target/hazard detection in previous fMRI studies (Ardekani et al., 2002; Clark et al., 2000; Crottaz-Herbette et al., 2005), were positively correlated with correct hits. In addition, these 2 areas exhibited less activation in association with increased alcohol intoxication. "
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ABSTRACT: Prior studies report that accidents involving intoxicated drivers are more likely to occur during performance of secondary tasks. We studied this phenomenon, using a dual-task paradigm, involving performance of a visual oddball (VO) task while driving in an alcohol challenge paradigm. Previous functional MRI (fMRI) studies of the VO task have shown activation in the anterior cingulate, hippocampus, and prefrontal cortex. Thus, we predicted dose-dependent decreases in activation of these areas during VO performance.
Forty healthy social drinkers were administered 3 different doses of alcohol, individually tailored to their gender and weight. Participants performed a VO task while operating a virtual reality driving simulator in a 3T fMRI scanner.
Analysis showed a dose-dependent linear decrease in Blood Oxygen Level Dependent activation during task performance, primarily in hippocampus, anterior cingulate, and dorsolateral prefrontal areas, with the least activation occurring during the high dose. Behavioral analysis showed a dose-dependent linear increase in reaction time, with no effects associated with either correct hits or false alarms. In all dose conditions, driving speed decreased significantly after a VO stimulus. However, at the high dose this decrease was significantly less. Passenger-side line crossings significantly increased at the high dose.
These results suggest that driving impairment during secondary task performance may be associated with alcohol-related effects on the above brain regions, which are involved with attentional processing/decision-making. Drivers with high blood alcohol concentrations may be less able to orient or detect novel or sudden stimuli during driving.
Alcoholism Clinical and Experimental Research 02/2009; 33(4):617-25. DOI:10.1111/j.1530-0277.2008.00876.x · 3.21 Impact Factor
Available from: Justine M Gatt
- "These concepts of selective attention and context updating are relevant to evidence for the involvement of the BDNF polymorphism in aspects of learning and memory (Egan et al., 2003; Poo, 2001; Tyler et al., 2001). Oddball stimuli have been found to elicit hippocampal activation in both intracranial P300 recordings (Halgren et al., 1980; Heit et al., 1990; McCarthy et al., 1989) and functional magnetic resonance imaging (fMRI) (Crottaz-Herbette et al., 2005; Kiehl et al., 2001; Williams et al., 2007; Yoshiura et al., 1999). However, there is also contrary evidence of P300 preservation despite unilateral hippocampal lesions (Jonson, 1989; Rugg et al., 1991). "
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ABSTRACT: In this study, we examined whether the Met allele of the BDNF Val66Met polymorphism is associated with selective disruptions to task-relevant information processing. In 475 non-clinical participants for whom BDNF genotype status was determined we used the 'IntegNeuro' computerized battery of neuropsychological tests to assess cognitive performance, an auditory oddball task to elicit the P300 event-related potential (ERP) and, in smaller subsets of these subjects, high resolution structural MRI imaging to quantify fronto-hippocampal grey matter (n=161), and functional magnetic resonance imaging to assess fronto-hippocampal BOLD activation (n=37). Met/Met (MM) homozygotes had higher verbal recall errors, in the absence of differences in attention, executive function, verbal ability or sensori-motor function. Further, MM homozygotes demonstrated a slowed P300 ERP during the oddball task, with corresponding alterations in hippocampal and lateral prefrontal activation, and a localized reduction in hippocampal grey matter. These results are consistent with a subtle impact of the Met allele on fronto-hippocampal systems involved in selective information processing of stimulus context and memory updating within the normal population. The findings also indicate that heritable endophenotypes such as the P300 have value in elucidating genotype-phenotype relationships.
Biological psychology 10/2008; 80(2):176-88. DOI:10.1016/j.biopsycho.2008.09.001 · 3.40 Impact Factor
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