Hemispheric Asymmetry for Encoding Unrelated Word Pairs? A Functional Near-infrared Spectroscopy Study / 航天医学与医学工程

Objective To explore the role of the prefrontal cortex in semantic encoding of unrelated word pairs by using functional near-infrared spectroscopy (fNIRS). Method Forty-eight subjects were presented unrelated pairs of Chinese words under both the nonsemantic and semantic encoding conditions. Under the nonsemantic condition, subjects judged whether the two words had similar orthographic structures; under the semantic condition, they generated a sentence involving the presented word pairs. The changes of regional blood volume associated with the cognitive tasks were measured by using fNIRS equipment which was a continuous optical imager. Result The regions that corresponded to the prefrontal regions showed greater activation under semantic than nonsemantic condition in both left and right hemispheres, although the extent of the activation was larger in the left than right prefrontal regions. This result was consistent with other neuroimaging studies on unrelated word pairs processing, but did not conform to the strict interpretations of the hemispheric encoding/retrieval asymmetry model (HERA). Conclusion This study suggests that material specificity is one of the important factors to influence hemispheric asymmetry in memory encoding. When associations between items are required, right prefrontal regions participate in the encoding processing as well. It also indicates that fNIRS imaging is a viable method of investigating higher level cognitive processing such as memory.

Left Prefrontal Cortex Activation during Semantic Encoding Accessed with Functional Near Infrared Imaging / 航天医学与医学工程

Objective To investigate the left prefrontal lobe activation during semantic and non-semantic encoding tasks with functional near-infrared imaging (fNIRI) technique. Method 22 healthy subjects were assigned semantic encoding and non-semantic encoding tasks. During semantic encoding tasks, subjects were asked to make a meaningful sentence including two unrelated Chinese word pairs, while during non-semantic encoding task they were asked to judge whether the two Chinese word pairs had the same morphological structure or not. Light intensity of two wavelengths (760 nm and 850 nm) diffused through skull and left prefrontal lobe were real-time recorded and used to reconstruct the brain activation image during the experiment. Result With the fNIRI, significant activations were observed in the left inferior prefrontal cortex (Brodmann' areas 45 and 47) during the two tasks, but the evoked activations were more significant for semantic than non-semantic task. These observations were consistent with the results reported by others with functional megnetic resonance imaging(fMRI) and positron-emission tomographyPET.Conclusion The results suggest that fNIRI provides an important, non-invasive way to map the prefrontal activation during cognitive tasks.

The Recovery of Memory after Traumatic Brain Injury / 中国临床心理学杂志

Objective:To explore the time course of memory recovery during post-traumatic amnesia after brain injury.Methods: A patient (WGS, aged 34) with lesions in the left temporal lobe was compared with four matched control subjects on various cognitive tests. These tests included Galveston Orientation and Amnesia test, Wechsler Memory Scale-Revised Test, Semantic Memory, and Remote Memory Test. WGS was tested at 20th days and 33rd days after the brain injury. Results: During the period of post-traumatic amnesia, marked recovery was observed for orientation, semantic memory and remote memory (especially the recent and the earlier items). While the recovery of learning for new knowledge was slow, learning curve of association of unrelated items was flat.Conclusion: The differential time courses for recovery of cognitive functions should be well considered in rehabilitative training after traumatic brain injury.