Bilateral Fusiform Cortex Research Articles

Neural similarities and differences between native and second languages in the bilateral fusiform cortex in Chinese-English bilinguals

In the field of bilingualism, researchers have proposed an assimilation hypothesis that posits that bilinguals apply the neural network of their native language to process their second language. In Chinese-English bilinguals, the bilateral fusiform gyrus has been identified as the key brain region showing the assimilation process. Specifically, in contrast to left-lateralized activation in the fusiform gyrus in native English speakers, Chinese-English bilinguals recruit the bilateral fusiform cortex to process English words as they do in the processing of Chinese characters. Nevertheless, it is unclear which type of information processing is assimilated in the fusiform gyrus. Using representational similarity analysis (RSA) and psychophysiological interaction (PPI) analysis, this study examined the differences in information representation and functional connectivity between both languages in the fusiform subregions in Chinese-English bilinguals. Univariate analysis revealed that both Chinese and English naming elicited strong activations in the bilateral fusiform gyrus, which confirmed the assimilation process at the activation intensity level. RSA indicated that the neural pattern of English phonological information was assimilated by Chinese in the anterior and middle right fusiform gyrus, while those of orthographic and visual form information were not. Further PPI analysis demonstrated that the neural representation of English phonological information in the right anterior fusiform subregion was related to its interaction with the frontotemporal areas for high-level linguistic processing, while the neural representation of English orthographic information in the right middle fusiform subregion was linked to its interaction with the left inferior occipital cortex for visual processing. These results suggest that, despite the recruitment of similar neural resources in one's native and second languages, the assimilation of information representation is limited in the bilateral fusiform cortex. Our results shed light on the neural mechanisms of second language processing.

The hippocampus shows an own-age bias during unfamiliar face viewing.

The present study investigated the neural correlates of the own-age bias for face recognition in a repetition suppression paradigm. Healthy young and older adults viewed upright and inverted unfamiliar faces. Some of the upright faces were repeated following one of two delays (lag 0 or lag 11). Repetition suppression effects were observed in bilateral fusiform cortex. However, there were no significant effects indicating an own-age bias in repetition suppression. The absence of these effects is arguably inconsistent with perceptual expertise accounts of own-age biases in face processing. By contrast, the right anterior hippocampus showed an own-age bias (greater activity for own-age compared to other-age faces) when viewing an unfamiliar face for the first time. Given the importance of the hippocampus for episodic memory encoding, we conjecture that the increased hippocampal activity for own-age relative to other-age faces reflects differential engagement of neural processes supporting the episodic encoding of faces and might provide insight into the neural underpinnings of own-age biases in face recognition memory.

Cross-Language Pattern Similarity in the Bilateral Fusiform Cortex Is Associated with Reading Proficiency in Second Language

Previous studies have found that native Chinese speakers recruit the bilateral fusiform gyrus to read English words, in the same manner as they read Chinese words (i.e., the assimilation process). In this study, we quantified the neural pattern similarity between native (L1) and second languages (L2) by using representational similarity analysis (RSA), and examined the modulatory effects of L2 proficiency on cross-language neural pattern similarity (PS) in the bilateral fusiform cortex. Results showed that, for Chinese–English bilinguals, higher reading proficiency in L2 was associated with greater cross-language PS in the left fusiform gyrus, but with lower PS in the right fusiform gyrus. These results suggest that, as L2 proficiency increases, the assimilation process is enhanced in the region for word reading (left fusiform gyrus), but reduced in the region for nonlinguistic processing (right fusiform gyrus).

Distinct and overlapping fusiform activation to faces and food

The fusiform cortex is a part of the ventral visual stream and is typically associated with face processing. Indeed, a subregion of the fusiform has been named the “fusiform face area” or FFA, based on its robust response to faces relative to other objects. In a separate literature, appetizing food has also been shown to activate bilateral fusiform cortex, yet no study to date has directly compared face and food responses within the same paradigm. Here, we use functional magnetic resonance imaging (fMRI) to compare face and food responses in ventral visual cortex and other regions that are typically associated with face processing. We present evidence that a region of the left fusiform cortex (typically associated with face processing) actually responds equally to faces and food. We go on to describe the similarities and differences in location of face- and food-responses in the fusiform, the relationship of fusiform activation to body mass index (BMI), and resting state connectivity of face- and food-selective fusiform. Results are interpreted within a model in which motivational relevance or value influence fusiform response.

An fMRI task for exploring memory effects of significant-other activation in social cognition

A novel functional magnetic resonance imaging (fMRI) paradigm for exploring the neurobiologic basis of a key aspect of social cognition was developed, adapted from Andersen’s transference paradigm (Andersen & Chen, 2002). This paradigm captures the extent to which current memory in relation to a stranger is impacted by activated knowledge of a significant other (SO). Forty healthy young adult participants were seen for two separate sessions and misled to believe that the sessions were unrelated to one another. In the first, participants listed descriptive sentences for each of four different important people in their lives (SOs), chose 20 irrelevant adjectives about each from a list, and provided descriptive sentences about 80 famous individuals. In the second session, at least two months later, participants were shown 20 sentences about each of six different supposed strangers (“targets”). Unbeknownst to participants, two of the targets resembled SOs described by the participant in the initial session (“the experimental targets”), two resembled SOs described by a different participant (the yoked-control), and two were constructed from a random assortment of sentences the participant listed about famous individuals (the no-representation control). The participants were then shown 30 sentences about each target and asked to rate how likely it was that they were just exposed to each about that particular target. For targets resembling SOs, 10 of the 30 sentences (the “lures”) had, in fact, not been seen previously about the target, but were from the participant’s own description of the pertinent SO. Therefore, participants should incorrectly rate these lures higher when the target resembled their own SO, as compared to the comparable lures in either control condition. Functional MRI images were collected during the entire second session using a GE Signa 3T whole body scanner. Individual and group level fMRI analyses were conducted using SPM8. Replicating Andersen’s findings, the average memory recognition score was higher for the “lures” in the SO condition (M =2.69; SD = .61) than for those in the yoked-control condition (M = 2.55; SD = .65), paired t (39) = 2.01, p = .05). In fMRI analyses, betas reflected the tendency of neural activity to increase when SO-relevant targets were presented during the learning phase and these were used to produce a second-level contrast map which showed significant differences in activation during the presentation of SO-resembling targets, in comparison with the yoked-control condition. Findings were significant at the level of p < .05 after correction for multiple comparisons using the false discovery rate method. Neural activity in bilateral fusiform cortex and the superior frontal gyrus increased during SO activation, while neural activity in the subgenual ACC (sgACC) decreased. This paradigm is a powerful tool for exploring the neural basis of social cognition and may well prove useful in characterizing psychiatric disorders in a developmentally sophisticated way. METHOD ● Participants 40 Healthy Young Adults Ages 18-30, mean=21.9 15 male, 25 female ● Initial Session ● Experimental Session ● Learning Task ● Memory Recognition Task RESULTS Fig 1. Statistically significant recognition memory effect, n=40, p=.05 Fig 2. Healthy control schema-relevant activity (red= increasing, blue=decreasing), N=40, corrected p<.05.  Selects 4 Significant Others and provides 10 positive and 10 negative short sentences about each  Identifies 25 “irrelevant” adjectives about each Significant Other  Provides 40 positive and 40 negative short sentences about 80 well-known individuals

Dissociation of mirroring and mentalising systems in autism

The role of mirror neuron systems and mentalising systems in causing poor social and communication skills in individuals with autistic spectrum conditions is hotly debated. We studied 18 adults with autistic spectrum conditions in comparison to 19 age and IQ matched typical individuals. Behavioural assessments revealed difficulties in mental state attribution and action comprehension in the autism sample. We examined brain responses when observing rational and irrational hand actions, because these actions engage mirror and mentalising components of the social brain respectively.Both typical and autistic participants activated the left anterior intraparietal sulcus component of the mirror system when viewing hand actions compared to moving shapes. The typical but not autistic participants activated the posterior mid cingulate cortex/supplementary motor area and bilateral fusiform cortex when viewing hand actions. When viewing irrational hand actions, the medial prefrontal cortex of typical participants deactivated but this region did not distinguish the different stimuli in autistic participants. These results suggest that parietal mirror regions function normally in autism, while differences in action understanding could be due to abnormal function of cingulate, fusiform and medial prefrontal regions. Thus, brain regions associated with mirroring and mentalising functions are differentially affected in autistic spectrum conditions.

Neural activity that predicts subsequent memory and forgetting: A meta-analysis of 74 fMRI studies

The present study performed a quantitative meta-analysis of functional MRI studies that used a subsequent memory approach. The meta-analysis considered both subsequent memory (SM; remembered>forgotten) and subsequent forgetting (SF; forgotten>remembered) effects, restricting the data used to that concerning visual information encoding in healthy young adults. The meta-analysis of SM effects indicated that they most consistently associated with five neural regions: left inferior frontal cortex (IFC), bilateral fusiform cortex, bilateral hippocampal formation, bilateral premotor cortex (PMC), and bilateral posterior parietal cortex (PPC). Direct comparisons of the SM effects between the studies using verbal versus pictorial material and item-memory versus associative-memory tasks yielded three main sets of findings. First, the left IFC exhibited greater SM effects during verbal material than pictorial material encoding, whereas the fusiform cortex exhibited greater SM effects during pictorial material rather than verbal material encoding. Second, bilateral hippocampal regions showed greater SM effects during pictorial material encoding compared to verbal material encoding. Furthermore, the left hippocampal region showed greater SM effects during pictorial-associative versus pictorial-item encoding. Third, bilateral PMC and PPC regions, which may support attention during encoding, exhibited greater SM effects during item encoding than during associative encoding. The meta-analysis of SF effects indicated they associated mostly with default-mode network regions, including the anterior and posterior midline cortex, the bilateral temporoparietal junction, and the bilateral superior frontal cortex. Recurrent activity oscillations between the task-positive and task-negative/default-mode networks may account for trial-to-trial variability in participants' encoding performances, which is a fundamental source of both SM and SF effects. Taken together, these findings clarify the neural activity that supports successful encoding, as well as the neural activity that leads to encoding failure.

Modulation of fusiform cortex activity by cholinesterase inhibition predicts effects on subsequent memory

Cholinergic influences on memory are likely to be expressed at several processing stages, including via well-recognized effects of acetylcholine on stimulus processing during encoding. Since previous studies have shown that cholinesterase inhibition enhances visual extrastriate cortex activity during stimulus encoding, especially under attention-demanding tasks, we tested whether this effect correlates with improved subsequent memory. In a within-subject physostigmine versus placebo design, we measured brain activity with functional magnetic resonance imaging while healthy and mild Alzheimer's disease subjects performed superficial and deep encoding tasks on face (and building) visual stimuli. We explored regions in which physostigmine modulation of face-selective neural responses correlated with physostigmine effects on subsequent recognition performance. In healthy subjects physostigmine led to enhanced later recognition for deep- versus superficially-encoded faces, which correlated across subjects with a physostigmine-induced enhancement of face-selective responses in right fusiform cortex during deep- versus superficial-encoding tasks. In contrast, the Alzheimer's disease group showed neither a depth of processing effect nor restoration of this with physostigmine. Instead, patients showed a task-independent improvement in confident memory with physostigmine, an effect that correlated with enhancements in face-selective (but task-independent) responses in bilateral fusiform cortices. Our results indicate that one mechanism by which cholinesterase inhibitors can improve memory is by enhancing extrastriate cortex stimulus selectivity at encoding, in a manner that for healthy people but not in Alzheimer's disease is dependent upon depth of processing.

Functional and morphometric brain dissociation between dyslexia and reading ability

In functional neuroimaging studies, individuals with dyslexia frequently exhibit both hypoactivation, often in the left parietotemporal cortex, and hyperactivation, often in the left inferior frontal cortex, but there has been no evidence to suggest how to interpret the differential relations of hypoactivation and hyperactivation to dyslexia. To address this question, we measured brain activation by functional MRI during visual word rhyme judgment compared with visual cross-hair fixation rest, and we measured gray matter morphology by voxel-based morphometry in dyslexic adolescents in comparison with (i) an age-matched group, and (ii) a reading-matched group younger than the dyslexic group but equal to the dyslexic group in reading performance. Relative to the age-matched group (n = 19; mean 14.4 years), the dyslexic group (n = 19; mean 14.4 years) exhibited hypoactivation in left parietal and bilateral fusiform cortices and hyperactivation in left inferior and middle frontal gyri, caudate, and thalamus. Relative to the reading-matched group (n = 12; mean 9.8 years), the dyslexic group (n = 12; mean 14.5 years) also exhibited hypoactivation in left parietal and fusiform regions but equal activation in all four areas that had exhibited hyperactivation relative to age-matched controls as well. In regions that exhibited atypical activation in the dyslexic group, only the left parietal region exhibited reduced gray matter volume relative to both control groups. Thus, areas of hyperactivation in dyslexia reflected processes related to the level of current reading ability independent of dyslexia. In contrast, areas of hypoactivation in dyslexia reflected functional atypicalities related to dyslexia itself, independent of current reading ability, and related to atypical brain morphology in dyslexia.

Language experience shapes fusiform activation when processing a logographic artificial language: An fMRI training study

The significant role of the left midfusiform cortex in reading found in recent neuroimaging studies has led to the visual word form area (VWFA) hypothesis. This hypothesis suggests that years of experience reading native language change the visual expertise of this region to be especially sensitive to the visual form of native language. The present study aimed at testing this hypothesis by exploring the role of language experience in shaping the fusiform activation. We designed a logographic artificial language (LAL) using the visual form and pronunciation of Korean Hangul characters (but their correspondence was shuffled) and assigning arbitrary meanings to these characters. Twelve native Chinese Mandarin speakers (6 male and 6 female, 18 to 21 years old) with no prior knowledge of Korean language were trained in the visual form of these characters for 2 weeks, followed by 2 weeks each of phonological and semantic training. Behavioral data indicated that training was effective in increasing the efficiency of visual form processing and establishing the connections among visual form, sounds, and meanings. Imaging data indicated that at the pre-training stage, subjects showed stronger activation in the fusiform regions for LAL than for Chinese across both one-back visual matching task and the passive viewing task. Visual form training significantly decreased the activation of bilateral fusiform cortex and the left inferior occipital cortex, whereas phonological training increased activation in these regions, and the right fusiform remained more active after semantic training. Increased activations after phonological and semantic training were also evident in other regions involved in language processing. These findings thus do not seem to be consistent with the visual-expertise-induced-sensitivity hypothesis about fusiform regions. Instead, our results suggest that visual familiarity, phonological processing, and semantic processing all make significant but different contributions to shaping the fusiform activation.

The neural origins of specific and general memory: the role of the fusiform cortex

Recognition of an object can be based on memory for specific details of a prior encounter with the object, or on a more general memory for the type of object previously encountered. Responding on the basis of general information alone can sometimes produce memory errors involving both distortion and forgetting, but little is known about the neural origins of general versus specific recognition. We extended the standard subsequent memory paradigm to examine whether neural activity at encoding predicts whether an object will subsequently elicit specific as compared to general memory. During event-related functional magnetic resonance imaging (fMRI), participants viewed objects and made size judgments about them. Later, they viewed same, similar, and new objects, labeling each as “same,” “similar,” or “new.” Specific recognition was indicated by a “same” response to a same object. By contrast, general, non-specific recognition was indicated by either a “same” response to a similar object (false memory) or a “similar” response to a same object (partial memory). As predicted, specific recognition, as compared to non-specific recognition, was associated with encoding-related activity in the right fusiform cortex, while non-specific recognition, as compared to forgetting, was associated with encoding-related activity in the left fusiform cortex. Furthermore, all successful recognition (specific and general), as compared to forgetting, was associated with encoding-related activity in bilateral fusiform cortex. These results suggest that the right fusiform cortex is associated with specific feature encoding, while the left fusiform cortex is involved in more general object encoding.

Brain Mechanisms for Detecting Perceptual, Semantic, and Emotional Deviance

The observation that we note the exceptional over the mundane has been the subject of extensive psychological and electrophysiological analysis in “oddball” paradigms. Whether detection of a sensory oddball reflects the operation of a generic mechanism or, alternatively, mechanisms sensitive to specific attributes of stimulus deviance is unknown. To address this question we used event-related functional MRI (fMRI) to measure neural responses during presentation of nouns, of which a proportion were perceptually, semantically, or emotionally deviant. Oddballs, regardless of deviant attributes and depth of processing, activated right inferior prefrontal and bilateral posterior fusiform cortices. Attribute-specific responses, independent of depth of processing, were evident in bilateral fusiform cortices for perceptual oddballs and left amygdala for emotional oddballs. By contrast, an interaction with depth of processing was evident in left prefrontal cortex for semantic oddballs. We conclude that detection of oddballs reflects the operation of a generic “deviance detection system,” involving right prefrontal and fusiform cortices in addition to specific brain regions sensitive to the stimulus attributes that determine the qualitative characteristics of deviance.