Summary: A new study shows both shared and distinct roles for the left and right sides of the brain in storing and retrieving semantic memory, with left-sided regions more critical for verbal naming and expression.

Study Overview

Researchers at the University of Manchester conducted the first comprehensive neuropsychological comparison of how the left and right anterior temporal lobes (ATLs) contribute to semantic memory. The study, led by Dr Grace Rice and Professor Matthew Lambon Ralph, examined verbal and visual aspects of semantic knowledge in patients who had undergone brain surgery to treat longstanding epilepsy. Funding was provided by the Engineering and Physical Sciences Research Council and the Medical Research Council.

Participants and Design

The team assessed 41 patients who had surgical removal of tissue in one anterior temporal lobe to control seizures. Of these, 21 patients had left anterior temporal lobe resections and 20 had right anterior temporal lobe resections. All patients experienced reduced seizure frequency after surgery and many regained everyday activities such as work and driving. The patients’ performance was compared with a control group of 20 people without neurological conditions.

Tests and Measures

To probe verbal semantic memory, participants completed tasks such as naming pictures and famous people, and matching words based on meaning. The famous-person naming task used well-known public figures as stimuli. To examine visual and face-related semantic processing, tests included recognition of facial familiarity and identifying emotions in photographs. The battery covered both expressive and receptive aspects of semantic knowledge, as well as object recognition and word comprehension.

outline of person — Patients were asked to identify emotions and judge whether faces were familiar as part of the visual semantic assessments. Image used with public domain attribution.

Key Findings

The results reveal that both ATLs contribute substantially to semantic memory across verbal and visual tasks, supporting a model in which the two hemispheres form a coupled bilateral system for representing conceptual knowledge. However, the study also found graded hemispheric specializations emerging from how each ATL connects with other brain regions involved in speech production and face perception.

Specifically, patients with left ATL resections showed greater difficulty on tasks requiring verbal expression of knowledge—especially naming and accessing meaning from written words. These deficits affected expressive and receptive verbal tasks, consistent with the left hemisphere’s stronger links to language production networks.

Patients with right ATL resections displayed relatively greater problems recognizing famous faces as familiar and in some visual recognition measures, although this effect was less consistent across all tests. Overall, both groups exhibited mild semantic impairments across naming, recognition, and emotion perception tasks, but the pattern of difficulties differed by side of surgery.

Interpretation and Implications

These findings reconcile prior inconsistent results by demonstrating a shared bilateral representation of semantic knowledge with graded hemispheric specializations. The left ATL appears particularly important when semantic retrieval must be expressed verbally, while the right ATL contributes more to nonverbal aspects such as face familiarity. The observed specializations likely reflect differential connectivity—left ATL’s links to speech production areas and right ATL’s links to face perception regions—rather than strictly isolated storage of separate types of knowledge.

The study has two important implications. Clinically, it clarifies the cognitive consequences of anterior temporal lobe resections performed to treat epilepsy, helping clinicians and patients anticipate and manage changes in naming and recognition abilities after surgery. Scientifically, the results advance our understanding of where and how semantic memories are represented in the brain, emphasizing a networked, bilateral architecture with graded lateralization.

Study Abstract (Condensed)

The research assessed multiple aspects of semantic cognition in postsurgical temporal lobe epilepsy patients who had left or right anterior temporal lobectomies (n = 41). Both groups showed deficits across expressive and receptive verbal tasks, object and word recognition, famous-face naming and recognition, and perception of faces and emotions. Left-resected patients were more impaired on tasks requiring naming or accessing information from written words; right-resected patients were relatively more impaired at recognizing famous faces as familiar. The findings support a model in which both ATLs act as a coupled bilateral system for semantic representation, with graded hemispheric specializations arising from differential connectivity to lateralized speech and face-processing regions.

Research and Source Information

Research lead: Dr Grace Rice and Professor Matthew Lambon Ralph, University of Manchester. Clinical collaborators included neuropsychology teams at Salford Royal and The Walton Centre for Neurology in Liverpool.

Publisher/organizer: NeuroscienceNews.com (article originally reporting the university research). Image credited to NeuroscienceNews.com and described as public domain.

Original research published open access in the journal Cerebral Cortex. DOI: 10.1093/cercor/bhx362

Citation

University of Manchester. “Can’t Remember a Name? Blame the Left Side of Your Brain.” NeuroscienceNews (2018).