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Timing of posterior parahippocampal gyrus activity reveals multiple scene processing stages.

ABSTRACT: Posterior parahippocampal gyrus (PPHG) is strongly involved during scene recognition and spatial cognition. How PPHG electrophysiological activity could underlie these functions, and whether they share similar timing mechanisms is unknown. We addressed this question in two intracerebral experiments which revealed that PPHG neural activity dissociated an early stimulus-driven effect (>200 and <500 ms) and a late task-related effect (>600 and <800 ms). Strongest PPHG gamma band (50-150 Hz) activities were found early when subjects passively viewed scenes (scene selectivity effect) and lately when they had to estimate the position of an object relative to the environment (allocentric effect). Based on single trial analyses, we were able to predict when patients viewed scenes (compared to other visual categories) and when they performed allocentric judgments (compared to other spatial judgments). The anatomical location corresponding to the strongest effects was in the depth of the collateral sulcus. Our findings directly affect current theories of visual scene processing and spatial orientation by providing new timing constraints and by demonstrating the existence of separable information processing stages in the functionally defined parahippocampal place area.

SUBMITTER: Bastin J

PROVIDER: S-EPMC6870532 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Timing of posterior parahippocampal gyrus activity reveals multiple scene processing stages.

Bastin Julien J Committeri Giorgia G Kahane Philippe P Galati Gaspare G Minotti Lorella L Lachaux Jean-Philippe JP Berthoz Alain A

Human brain mapping 20120130 6

Posterior parahippocampal gyrus (PPHG) is strongly involved during scene recognition and spatial cognition. How PPHG electrophysiological activity could underlie these functions, and whether they share similar timing mechanisms is unknown. We addressed this question in two intracerebral experiments which revealed that PPHG neural activity dissociated an early stimulus-driven effect (>200 and <500 ms) and a late task-related effect (>600 and <800 ms). Strongest PPHG gamma band (50-150 Hz) activit ...[more]

PMID: 22287281

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Project description:BackgroundTinnitus can interfere with a patient's speech discrimination, but whether tinnitus itself or the accompanying sensorineural hearing loss (SNHL) causes this interference is still unclear. We analyzed event-related electroencephalograms (EEGs) to observe auditory-related brain function and explore the possible effects of SNHL on auditory processing in tinnitus patients.MethodsSpeech discrimination scores (SDSs) were recorded in 21 healthy control subjects, 24 tinnitus patients, 24 SNHL patients, and 27 patients with both SNHL and tinnitus. EEGs were collected under an oddball paradigm. Then, the mismatch negativity (MMN) amplitude and latency, the clustering coefficient and average path length of the whole network in the tinnitus and SNHL groups were compared with those in the control group. Additionally, we analyzed the intergroup differences in functional connectivity among the primary auditory cortex (AC), parahippocampal gyrus (PHG), and inferior frontal gyrus (IFG).ResultsSNHL patients with or without tinnitus had lower SDSs than the control subjects. Compared with control subjects, tinnitus patients with or without SNHL had decreased MMN amplitudes, and SNHL patients had longer MMN latencies. Tinnitus patients without SNHL had a smaller clustering coefficient and a longer whole-brain average path length than the control subjects. SNHL patients with or without tinnitus had a smaller clustering coefficient and a longer average path length than patients with tinnitus alone. The connectivity strength from the AC to the PHG and IFG was lower on the affected side in tinnitus patients than that in control subjects; the connectivity strength from the PHG to the IFG was also lower on the affected side in tinnitus patients than that in control subjects. However, the connectivity strength from the IFG to the AC was stronger in tinnitus patients than that in the control subjects. In SNHL patients with or without tinnitus, these changes were magnified.ConclusionChanges in auditory processing in tinnitus patients do not influence SDSs. Instead, SNHL might cause the activity of the AC, PHG and IFG to change, resulting in impaired speech recognition in tinnitus patients with SNHL.

Project description:Human retrosplenial complex (RSC), located in medial parietal cortex, has been implicated in numerous cognitive functions, including scene perception, spatial navigation, and autobiographical memory retrieval. Recently, a posterior-anterior distinction within RSC was proposed, such that posterior aspects process scene-related visual information (constituting a medial place area [MPA]), whereas anterior aspects process information that is vividly retrieved from memory, thereby supporting remembering and potentially navigation. Here, we tested this proposed distinction in a single group of participants (both male and female) using fMRI with both perceptual and mnemonic tasks. After completing a resting-state scan, participants performed a task that required constructing scenes from memory and completed a scene selectivity localizer task. We tested directly perceptual and mnemonic responses in MPA and an anterior, connectivity-defined region (CON), which showed strong functional connectivity with anterior parahippocampal place area. A double dissociation was observed, such that CON was more strongly activated during scene construction than was MPA, whereas MPA was more perceptually responsive than CON. Further, peak responses from the scene construction task were anterior to perceptual peaks in all but 1 participant and hemisphere. Finally, through analyses of the posterior-anterior response profiles, we identify the fundus of the parieto-occipital sulcus as a potential location for the crossover from perceptual to mnemonic representations and highlight a potential left-hemisphere advantage for mnemonic representations. Collectively, our results support a distinction between posterior and anterior aspects of the RSC, suggesting that more specific functional-anatomic terms should be used in its place in future work.SIGNIFICANCE STATEMENT The retrosplenial complex (RSC) has been implicated in vision, spatial cognition, and memory. We previously speculated on a potential posterior-anterior distinction within RSC for scene perception and memory-based scene construction/navigation. Here, we tested this distinction through a combination of resting-state, perceptual, and mnemonic task data. Consistent with our predictions, we demonstrate that perceptual responses peak consistently posterior of those elicited by memory-based scene construction within the broader RSC. Further, we highlight (1) the fundus of the parieto-occipital sulcus as a landmark for the transition between these representations, (2) the anterior bank of parieto-occipital sulcus as the point of maximal separation between these representations, and (3) identify a potential hemispheric asymmetry in mnemonic representations. These data support functional dissociations within RSC.

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Timing of posterior parahippocampal gyrus activity reveals multiple scene processing stages.

Publications

Timing of posterior parahippocampal gyrus activity reveals multiple scene processing stages.

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