Biomedical subjects

J Stephen Higgins

Publications and source records attributed to J Stephen Higgins.

4 recordsLinked to original sources

PubMed2006

Differential parahippocampal and retrosplenial involvement in three types of visual scene recognition.

Human observers can quickly and accurately interpret the meaning of complex visual scenes. The neural mechanisms underlying this ability are largely unexplored. We used functional magnetic resonance imaging to measure cortical activity while subjects identified briefly presented scenes as specific familiar locations ("Houston Hall"), general place categories ("kitchen"), or general situational categories ("party"). Scene-responsive voxels in the parahippocampal place area (PPA) and retrosplenial cortex (RSC) were highly sensitive to recognition level when identifying scenes, responding more strongly during location identification than during place category or situation identification. In contrast, the superior temporal sulcus, cingulate sulcus, and supermarginal gyrus displayed the opposite pattern, responding more strongly during place category and situation identification. Consideration of results from 4 experiments suggests that the PPA represents the visuospatial structure of individual scenes, whereas RSC supports processes that allow scenes to be localized within a larger extended environment. These results suggest that different scene identification tasks tap distinct cortical networks. In particular, we hypothesize that the PPA and RSC are critically involved in the identification of specific locations but play a less central role in other scene recognition tasks.

Adult↗

PubMed2005

Cortical correlates of face and scene inversion: a comparison.

Face recognition is more strongly impaired by stimulus inversion than nonface object recognition. This phenomenon, known as the face inversion effect (FIE), suggests that the visual system contains specialized processing mechanisms that are more engaged by upright faces than by inverted faces or nonface objects. Neuroimaging and neuropsychological studies indicate that environmental scenes may also recruit specialized-purpose processing machinery but a comparable inversion effect for scenes has not been established. Here we demonstrate that both face and scene inversion lead to behavioral penalties during performance of a continuous visual matching task; however, the scene inversion effect was less robust and declined in magnitude over the course of the experiment. Scene inversion led to greater neural response in the functionally defined lateral occipital (LO) object area for inverted versus upright scenes and reduced response in the parahippocampal place area (PPA), while face inversion lead to greater response in LO and the right middle fusiform (MF) object area for inverted versus upright faces but no change in the fusiform face area (FFA). A whole-brain analysis revealed several regions that responded more strongly to either upright versus inverted faces or upright versus inverted scenes, some of which may be involved in post-recognition processing. These results demonstrate that both face and scene inversion cause a shift from specialized processing streams towards generic object-processing mechanisms; however, this shift only leads to a reliable behavioral penalty in the case of face inversion.

Adolescent↗

PubMed2005

Learning places from views: variation in scene processing as a function of experience and navigational ability.

Humans and animals use information obtained from different viewpoints to form representations of the spatial structure of the world. We used functional magnetic resonance imaging (fMRI) adaptation to investigate the neural basis of this learning process and to show how the concomitant representations vary across individuals as a function of navigational ability. In particular, we examined the effect of repeating viewpoint and/ or place information over both short (within-trial) and long (across-scan) intervals on the neural response in scene processing regions. Short-term fMRI adaptation effects in the parahippocampal cortex were initially highly viewpoint-specific but became less so over time. Long-term fMRI repetition effects included a significant viewpoint-invariant component. When individual differences in navigational ability were considered, a significant correlation between the strength of these effects and self-reported navigational competence was observed. In particular, good navigators encoded representations that differed between new and old views and new and old places, whereas bad navigators did not. These results suggest that cortical scene representations evolve over time to become more viewpoint-invariant and that the quality of these representations directly impacts navigational ability.

Adult↗

PubMed2003

Nicotine enhances contextual fear conditioning in C57BL/6J mice at 1 and 7 days post-training.

Nicotine has been demonstrated to enhance learning processes. The present experiments extend these results to examine the effects of nicotine on acquisition and consolidation of contextual and cued fear conditioning, and the duration of nicotine's enhancement of conditioned fear. C57BL/6 mice were trained with two pairings of an auditory CS and a foot shock US. Multiple doses of nicotine were given before or immediately after training and on testing day (0.0, 0.050, 0.125, 0.250, and 0.375 mg/kg, i.p). Freezing to both the context and auditory CS was measured 24h after training and again 1 week after training. Mice did not receive nicotine for the 1-week retest. Nicotine (0.125 and 0.250 mg/kg) given on both training and testing days enhanced freezing to the context at 24h. In addition, elevated freezing to the context was seen 1 week post-training in mice previously treated with 0.125 and 0.250 mg/kg nicotine. Thus, nicotine-treated mice did show elevated levels of freezing when retested 1 week later, even though no nicotine was administered at the 1-week retest. Mice that received nicotine on training day or testing day only and mice that received nicotine with mecamylamine, a nicotinic receptor antagonist, were not different from saline-treated mice. In addition, post-training administration of nicotine did not enhance fear conditioning. The present results indicate that nicotine enhancement of contextual fear conditioning depends on administration of nicotine on training and test days but results in a long-lasting enhancement of memories of contextual fear conditioning that remains in the absence of nicotine.

Age Factors↗