The amodal system for conscious word and picture identification in the absence of a semantic task.
Leen Van Doren, Patrick Dupont, Sophie De Grauwe, Ronald Peeters, Rik Vandenberghe
Neuroimage December 29, 2009 DOI: 10.1016/j.neuroimage.2009.12.005 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | fMRI experiment Peer reviewed |
|---|---|
| Sample size | 28 |
| Population | Adult participants in two fMRI experiments (28 in experiment 1, 19 in experiment 2) |
| Keywords | Nerve net Humans Magnetic resonance imaging Brain mapping Consciousness Cues Pattern recognition, visual Reading Semantics Female Young adult |
| Key findings | For both words and pictures, activity in left occipitotemporal sulcus and inferior frontal sulcus tracked conscious identification and predicted later memory retrieval, with effective connectivity between inferior frontal sulcus and modality-specific systems mainly mediated via occipitotemporal sulcus. The authors argue this amodal involvement extends to tasks with minimal semantic executive demands. |
Abstract
Previous studies using explicit semantic tasks, such as category or similarity judgments, have revealed considerable neuroanatomical overlap between processing of the meaning of words and pictures. This result may have been influenced by the semantic executive control required by such tasks. We examined the degree of overlap while minimizing semantic executive demands. In a first fMRI experiment (n=28), we titrated word (35.3 ms, SD=9.6) and picture presentation duration (50.7 ms, SD=15.8) such that conscious stimulus identification became a stochastic process, with a 50% chance of success. Subjects had to indicate by key press whether or not they had been able to identify the stimulus. In a second fMRI experiment (n=19), the identification runs were followed by a surprise forced-choice recognition task and events were sorted on the basis of subsequent memory retrieval success rather than a subjective consciousness report. For both words and pictures, when stimulus processing exceeded the conscious identification threshold, the left occipitotemporal sulcus (OTS), intraparietal sulcus, inferior frontal junction, and middle third of the inferior frontal sulcus (IFS) were more active than when subjects had been unable to identify the stimulus. For both words and pictures, activity in two of these regions, IFS and OTS, predicted subsequent memory retrieval success. A Bayesian comparison revealed that the effective connectivity between IFS and the word- or picture-specific systems was mainly mediated via its connections with OTS. The amodal nature of left OTS and IFS involvement in word and picture processing extends to tasks with minimal semantic executive demands.