Stroke Research & Therapy

Description        

Because of their semantic dimensions of familiarity, ambiguity, decomposability, and transparency, idioms are distinct from other types of figurative language. The brain's processing of idioms has been the subject of numerous investigations. One of them is studying clinical populations. Studies on people who have aphasia, which is typically caused by damage to a complex language network that includes the main language areas in the Left Hemisphere of the brain, have provided support for this theory. Aphasic patients may exhibit selective impairment in the comprehension of idioms. This suggests that there are idioms that are less difficult to comprehend that do not solely rely on the LH of the brain. However, recent research does not appear to agree on when and if the kinds of idioms and tasks used play a significant role in this preference. The prisma method was used to conduct a systematic review. Articles were retained for further analysis based on an initial finding and after applying inclusion and exclusion criteria. Differences and similarities between studies were extracted, particularly with regard to patient characteristics, lesion location, the stimuli and tasks used, and language comprehension patterns. According to the findings, research on idiom comprehension in aphasia is marked by a wide range of experimental tasks and idiomatic stimulus types.

Different Testing Controversial Language Outcomes

 The interpretation of idiom comprehension patterns in aphasia across studies is unclear because of heterogeneity in these crucial aspects. Additionally, the descriptions of idiomatic stimuli were sometimes accompanied by terminological inconsistencies, and there was insufficient description of the idiomatic stimuli's nature and, more specifically, their semantic dimensions. Furthermore, language comprehension patterns were reported after treating patients with aphasia as a homogeneous group, regardless of their aphasic syndrome, and patient profiles were occasionally incomplete. Last but not least, the analysis of language comprehension patterns, patient profiles, experimental stimuli, and recommendations for future research are all included. These features set idiom processing apart from literal expressions and other forms of figurative language, such as puns, proverbs, and metaphors, Papagno. Compositional processes, in which the various meanings of the constituent words are combined to reach an overall meaning, are primarily responsible for literacy language comprehension. However, this is not the case with idioms. An idiom's constituent words cannot be combined to reach to the overall meaning. For example, the meanings of the constituent words of the idiom cannot be combined to reach the figurative meaning. The inherent semantic dimensions the idioms bear are thought to modulate how idioms are processed in the brain. Differences in comprehension patterns for PWA have been observed across studies, but it is still not certain what causes them. For example, some types of idioms may appear more and other less impaired for PWA. Papagno points out that variability in performance among PWA can occur for various reasons. The author points to two factors in specific the effect of the type of idioms-based on their different semantic dimensions- and the effect of the task type used across studies. Next, concerning the task type used across studies, different testing paradigms can be linked to controversial language outcomes. Most studies use a word or picture matching task. More specifically, a string-to-picture matching task presents participants with an idiom and usually three or four pictorial representations. Often, one represents the figurative meaning, one is a literally related meaning and one or two options represent an unrelated situation. This type of testing has been mostly used for ambiguous idioms. However, there has been evidence suggesting that the overt pictorial representation of a literally related meaning shows strong interference effects, similar to a Stroop effect. Consequently, even if patients are generally capable of reaching the figurative interpretation, they are blocked by the incapability of inhibiting the literal representation. In a similar line, a string-to-word matching test, presents participants with an idiom and usually three or four words expressions. Often, one represents the figurative meaning, one is the literal meaning or a semantic associate and the rest are unrelated options. Papagno mentions that the use of a semantic associate, instead of a literally related option, can reduce the interference effect and improve patients' performance in ambiguous idioms comprehension. Interestingly, in the case of unambiguous idioms, patients tend to have more “unrelated” errors. Both types of idioms as well as the type of task used can jointly affect patients' performance patterns. Up to now, there is not enough evidence suggesting which parameters are linked to a more favorable performance and which to a less.

Structural Changes Achieved Using Diffusion

 It is therefore important to disentangle how idiom type and task type can co-influence idiom comprehension. Such an endeavor aims at gaining a better understanding of idiom processing as well as of its neural correlates, from an anatomical point of view, by focusing on pathological populations such as patients suffering from aphasia. Quantification of white matter structural changes can be achieved using diffusion tensor imaging, where multiple measures can be extracted from the tensor model. Fractional anisotropy and mean diffusivity are the most frequently used measures. FA represents the directionality of water diffusion, regardless the rate. Whilst MD represents the rate of diffusion within a voxel. Other measures such as axial diffusivity and radial diffusivity can disentangle additional information as they reveal the apparent water diffusivity in the direction parallel and perpendicular to the main direction of diffusion within a voxel, respectively. Thus, they provide better characterization of the changes in WM properties which in turn help to elucidate the underlying pathology.