The Emotional Facet of Subjective and Neural Indices of Similarity.

Emotional similarity refers to the tendency to group stimuli together because they evoke the same feelings in us. The majority of research on similarity perception that has been conducted to date has focused on non-emotional stimuli. Different models have been proposed to explain how we represent semantic concepts, and judge the similarity among them. They are supported from behavioural and neural evidence, often combined by using Multivariate Pattern Analyses. By contrast, less is known about the cognitive and neural mechanisms underlying the judgement of similarity between real-life emotional experiences. This review summarizes the major findings, debates and limitations in the semantic similarity literature. They will serve as background to the emotional facet of similarity that will be the focus of this review. A multi-modal and overarching approach, which relates different levels of neuroscientific explanation (i.e., computational, algorithmic and implementation), would be the key to further unveil what makes emotional experiences similar to each other

Action understanding requires the left inferior frontal cortex.

Numerous studies have established that inferior frontal cortex is active when hand actions are planned, imagined, remembered, imitated, and even observed. Furthermore, it has been proposed that these activations reflect a process of simulating the observed action to allow it to be understood and thus fully perceived. However, direct evidence for a perceptual role for left inferior frontal cortex is rare, and linguistic or motor contributions to the reported activations have not been ruled out. We used repetitive transcranial magnetic stimulation (rTMS) over inferior frontal gyrus during a perceptual weight-judgement task to test the hypothesis that this region contributes to action understanding. rTMS at this site impaired judgments of the weight of a box lifted by a person, but not judgements of the weight of a bouncing ball or of stimulus duration, and rTMS at control sites had no impact. This demonstrates that the integrity of left inferior frontal gyrus is necessary to make accurate perceptual judgments about other people's actions

The role of the anterior temporal lobes in the comprehension of concrete and abstract words: rTMS evidence

Conceptual knowledge allows us to bring meaning to our world. Studies of semantic dementia (SD) patients and some functional neuroimaging studies indicate that the anterior temporal lobes, bilaterally, are a core neural substrate for the formation of conceptual representations. The majority of SD patients (who have circumscribed atrophy of the anterior temporal lobes) have better comprehension of concrete than abstract words. However, this finding remains controversial, as some individual SD patients have exhibited reverse imageability effects, i.e., relative preservation of abstract knowledge. This would imply that the anterior temporal lobes are particularly crucial for processing sensory aspects of semantic knowledge, which are an important part of concrete but not abstract concepts. To adjudicate on this debate, we used offline, low-frequency, repetitive transcranial magnetic stimulation to disrupt neural processing temporarily in the left or right temporal poles (TPs). We examined this effect using a synonym judgement task, comprising high, medium and low imageability items, which we have previously employed with a case-series of SD patients. The time required to make semantic decisions was slowed considerably, particularly for low imageability items, consistent with the pattern we observed in SD. These results confirm that both TPs make a critical contribution to semantic processing, even for abstract concepts that do not have strong sensory representations

Conceptual knowledge is underpinned by the temporal pole bilaterally: Convergent evidence from rTMS

Conceptual knowledge provides the basis on which we bring meaning to our world. Studies of semantic dementia patients and some functional neuroimaging studies indicate that the anterior temporal lobes, bilaterally, are the core neural substrate for the formation of semantic representations. This hypothesis remains controversial, however, as traditional neurological models of comprehension do not posit a role for these regions. To adjudicate on this debate, we conducted 2 novel experiments that used off-line, low-frequency, repetitive transcranial magnetic stimulation to disrupt neural processing temporarily in the left or right temporal poles (TPs). The time required to make semantic decisions was slowed considerably, yet specifically, by this procedure. The results confirm that both TPs form a critical substrate within the neural network that supports conceptual knowledge

Symmetry in Emotional and Visual Similarity between Neutral and Negative Faces

From MDPI via Jisc Publications RouterHistory: accepted 2021-10-31, pub-electronic 2021-11-04Publication status: PublishedIs Mr. Hyde more similar to his alter ego Dr. Jekyll, because of their physical identity, or to Jack the Ripper, because both evoke fear and loathing? The relative weight of emotional and visual dimensions in similarity judgements is still unclear. We expected an asymmetric effect of these dimensions on similarity perception, such that faces that express the same or similar feeling are judged as more similar than different emotional expressions of same person. We selected 10 male faces with different expressions. Each face posed one neutral expression and one emotional expression (five disgust, five fear). We paired these expressions, resulting in 190 pairs, varying either in emotional expressions, physical identity, or both. Twenty healthy participants rated the similarity of paired faces on a 7-point scale. We report a symmetric effect of emotional expression and identity on similarity judgements, suggesting that people may perceive Mr. Hyde to be just as similar to Dr. Jekyll (identity) as to Jack the Ripper (emotion). We also observed that emotional mismatch decreased perceived similarity, suggesting that emotions play a prominent role in similarity judgements. From an evolutionary perspective, poor discrimination between emotional stimuli might endanger the individual

Posterior middle temporal gyrus is involved in verbal and non-verbal semantic cognition:Evidence from rTMS

Background: Left posterior middle temporal gyrus (pMTG) is reliably activated in functional neuroimaging studies of semantic processing and is frequently damaged in patients with comprehension impairments following stroke (e.g., Wernicke's aphasia). Its precise function remains elusive, however. Some researchers take the view that pMTG is a multimodal semantic area, involved in verbal and non-verbal semantic cognition. Others ascribe a lexical-semantic function to the region, positing that it is involved in mapping between phonology and conceptual knowledge. Aims: We investigated whether pMTG was involved in non-verbal as well as verbal semantic cognition by using rTMS to induce temporary, focal “virtual lesions” to this region in healthy participants. Methods & Procedures: Participants completed picture and word versions of a semantic association test before and after receiving 10 minutes of 1-Hz offline rTMS to left pMTG. They also completed a difficulty-matched visual decision task on scrambled pictures. An occipital lobe control site was stimulated in a separate session. Outcomes & Results: TMS slowed responses to word and picture versions of the test to an equal degree. There was no slowing on a non-semantic visual-matching task, or following TMS to the control site. Conclusions: These results indicate that pMTG is involved in both verbal and non-verbal semantic cognition. This region could be key to understanding the multimodal semantic deficits often observed following stroke

The nature and neural correlates of semantic association vs. conceptual similarity

The ability to represent concepts and the relationships between them is critical to human cognition. How does the brain code relationships between items that share basic conceptual properties (e.g., dog and wolf) while simultaneously representing associative links between dissimilar items that co-occur in particular contexts (e.g., dog and bone)? To clarify the neural bases of these semantic components in neurologically intact participants, both types of semantic relationship were investigated in an fMRI study optimized for anterior temporal lobe (ATL) coverage. The clear principal finding was that the same core semantic network (ATL, superior temporal sulcus, ventral prefrontal cortex) was equivalently engaged when participants made semantic judgments on the basis of association or conceptual similarity. Direct comparisons revealed small, weaker differences for conceptual similarity > associative decisions (e.g., inferior prefrontal cortex) and associative > conceptual similarity (e.g., ventral parietal cortex) which appear to reflect graded differences in task difficulty. Indeed, once reaction time was entered as a covariate into the analysis, no associative versus category differences remained. The paper concludes with a discussion of how categorical/feature-based and associative relationships might be represented within a single, unified semantic system