Generalization of a Novel, Implicit Treatment for Coarse Coding Deficit in Right Hemisphere Brain Damage: A Single Subject Experiment

Voxel-Based Lesion Symptom Mapping of Coarse Coding and Suppression Deficits in Patients With Right Hemisphere Damage

PURPOSE

This study examined right hemisphere (RH) neuroanatomical correlates of lexical-semantic deficits that predict narrative comprehension in adults with RH brain damage. Coarse semantic coding and suppression deficits were related to lesions by voxel-based lesion symptom mapping.

METHOD

Participants were 20 adults with RH cerebrovascular accidents. Measures of coarse coding and suppression deficits were computed from lexical decision reaction times at short (175 ms) and long (1000 ms) prime-target intervals. Lesions were drawn on magnetic resonance imaging images and through normalization were registered on an age-matched brain template. Voxel-based lesion symptom mapping analysis was applied to build a general linear model at each voxel. Z score maps were generated for each deficit, and results were interpreted using automated anatomical labeling procedures.

RESULTS

A deficit in coarse semantic activation was associated with lesions to the RH posterior middle temporal gyrus, dorsolateral prefrontal cortex, and lenticular nuclei. A maintenance deficit for coarsely coded representations involved the RH temporal pole and dorsolateral prefrontal cortex more medially. Ineffective suppression implicated lesions to the RH inferior frontal gyrus and subcortical regions, as hypothesized, along with the rostral temporal pole.

CONCLUSION

Beyond their scientific implications, these lesion-deficit correspondences may help inform the clinical diagnosis and enhance decisions about candidacy for deficit-focused treatment to improve narrative comprehension in individuals with RH damage.

Contextual Constraint Treatment for coarse coding deficit in adults with right hemisphere brain damage: generalisation to narrative discourse comprehension

Coarse coding is the activation of broad semantic fields that can include multiple word meanings and a variety of features, including those peripheral to a word's core meaning. It is a partially domain-general process related to general discourse comprehension and contributes to both literal and non-literal language processing. Adults with damage to the right cerebral hemisphere (RHD) and a coarse coding deficit are particularly slow to activate features of words that are relatively distant or peripheral. This manuscript reports a pre-efficacy study of Contextual Constraint Treatment (CCT), a novel, implicit treatment designed to increase the efficiency of coarse coding with the goal of improving narrative comprehension and other language performance that relies on coarse coding. Participants were four adults with RHD. The study used a single-subject controlled experimental design across subjects and behaviours. The treatment involved pre-stimulation, using a hierarchy of strong and moderately biased contexts, to prime the intended distantly related features of critical stimulus words. Three of the four participants exhibited gains in auditory narrative discourse comprehension, the primary outcome measure. All participants exhibited generalisation to untreated items. No strong generalisation to processing non-literal language was evident. The results indicate that CCT yields both improved efficiency of the coarse coding process and generalisation to narrative comprehension.

An evidence-based systematic review on communication treatments for individuals with right hemisphere brain damage

PURPOSE

The purpose of this review is to evaluate and summarize the research evidence related to the treatment of individuals with right hemisphere communication disorders.

METHOD

A comprehensive search of the literature using key words related to right hemisphere brain damage and communication treatment was conducted in 27 databases (e.g., PubMed, CINAHL). On the basis of a set of pre-established clinical questions, inclusion/exclusion criteria, and search parameters, studies investigating sentence- or discourse-level treatments were identified and evaluated for methodological quality. Data regarding participant, intervention, and outcome variables were reported.

RESULTS

Only 5 studies were identified, each representing a different sentence- or discourse-level treatment approach and reporting a wide range of prosodic, expressive, receptive, and pragmatic outcomes.

CONCLUSION

Although the state of the evidence pertaining to right hemisphere communication treatments is at a very preliminary stage, some positive findings were identified to assist speech-language pathologists who are working with individuals with right hemisphere brain damage. Clinical implications and recommendations for future research are explored.