Activation In Bilateral Inferior Frontal Gyri Research Articles

Effects of highly purified cannabidiol (CBD) on fMRI of working memory in treatment-resistant epilepsy

ObjectiveWe aimed to determine changes in working memory and functional connectivity via functional magnetic resonance imaging (fMRI)-modified Sternberg task after treatment with highly purified cannabidiol (CBD, Epidiolex®; 100 mg/mL) in patients with treatment-resistant epilepsy (TRE). MethodsTwenty patients with TRE (mean age: 35.8 years; 7 male) performed fMRI Sternberg task before receiving CBD (“PRE”) and after reaching stable dosage of CBD (15–25 mg/kg/day; “ON”). Each patient performed 2 runs of the modified Sternberg task during PRE and ON fMRI. Twenty-three healthy controls (HCs; mean age: 25 years; 11 M) also completed the task. All were presented with a sequence of 2 or 6 letters and instructed to remember them (encoding). After a delay, a single letter was shown, and participants recalled if letter was shown in sequence (retrieval). Paired t-tests were used to analyze accuracy/response times. For each subject, event-related modeling of encoding (2 and 6 letters) and retrieval was performed. Paired t-tests controlling for seizure frequency change and scanner type were performed to assess changes in neural recruitment during encoding and retrieval in key regions of interest. ResultsThere was nonsignificant increase in mean modified Sternberg task accuracy from PRE to ON-CBD (28.6 vs. 32.1%). PRE and ON accuracy was worse than HCs (75.5%, p < 0.001). ON-PRE comparison revealed increased activation in the right inferior frontal gyrus (IFG) during 6-letter encoding. ON-HC comparison revealed increased activation in bilateral IFG and insula during 2-letter encoding. PRE-HC comparison revealed decreased activation in the left middle frontal gyrus during 6-letter encoding. None of these activations were associated with working memory performance. SignificanceTreatment-resistant epilepsy results in poorer working memory performance and lower neural recruitment compared with HCs. Treatment with CBD results in no significant changes in working memory performance and in significant increases in neural activity in regions important for verbal memory and attention compared with HCs during memory encoding.

Treatment-related changes in neural activation vary according to treatment response and extent of spared tissue in patients with chronic aphasia

Neuroimaging studies of aphasia recovery have linked treatment-related improvements in language processing to changes in functional brain activation in left hemisphere language regions and their right hemisphere homologues. Although there is some consensus that better behavioral outcomes are achieved when activation is restored to the left hemisphere, the circumstances that dictate how and why regions in both hemispheres respond to naming therapy are still unclear. In this study, an fMRI picture-naming task was used to examine 16 regions of interest in 26 patients with chronic aphasia before and after 12 weeks of semantic naming treatment. Ten control patients who did not receive treatment and 17 healthy controls were also scanned. Naming therapy resulted in a significant increase in cortical activation, an effect that was largely driven by patients who responded most favorably to treatment, as patients who responded less favorably (as well as those who did not receive treatment) had little change in activation over time. Relative to healthy controls, patients had higher pre-treatment activation in the bilateral inferior frontal gyri (IFG) and lower activation in the bilateral angular gyri; after treatment, they had higher activation in bilateral IFG, as well as in the right middle frontal gyrus. These results suggest that the predominant effect of beneficial naming treatment was an upregulation of traditional language areas and their right hemisphere homologues and, in particular, regions associated with phonological and semantic/executive semantic processing, as well as broader domain general functions. Additionally, in some left hemisphere regions, post-treatment changes in activation were greater when there was more damage than when there was less damage, indicating that spared tissue in otherwise highly damaged regions can be modulated by treatment.

Language structure in the brain: A fixation-related fMRI study of syntactic surprisal in reading

How is syntactic analysis implemented by the human brain during language comprehension? The current study combined methods from computational linguistics, eyetracking, and fMRI to address this question. Subjects read passages of text presented as paragraphs while their eye movements were recorded in an MRI scanner. We parsed the text using a probabilistic context-free grammar to isolate syntactic difficulty. Syntactic difficulty was quantified as syntactic surprisal, which is related to the expectedness of a given word's syntactic category given its preceding context. We compared words with high and low syntactic surprisal values that were equated for length, frequency, and lexical surprisal, and used fixation-related (FIRE) fMRI to measure neural activity associated with syntactic surprisal for each fixated word. We observed greater neural activity for high than low syntactic surprisal in two predicted cortical regions previously identified with syntax: left inferior frontal gyrus (IFG) and less robustly, left anterior superior temporal lobe (ATL). These results support the hypothesis that left IFG and ATL play a central role in syntactic analysis during language comprehension. More generally, the results suggest a broader cortical network associated with syntactic prediction that includes increased activity in bilateral IFG and insula, as well as fusiform and right lingual gyri.

Cognitive empathy modulates the processing of pragmatic constraints during sentence comprehension

Previous studies have shown that brain regions for mentalizing, including temporoparietal junction (TPJ) and medial prefrontal cortex (mPFC), are activated in understanding the nonliteral meaning of sentences. A different set of brain regions, including left inferior frontal gyrus (IFG), is activated for dealing with pragmatic incongruence. Here we demonstrate that individuals' cognitive empathic ability modulates the brain activity underlying the processing of pragmatic constraints during sentence comprehension. The lian … dou … construction in Chinese (similar to English even) normally describes an event of low expectedness; it also introduces a pragmatic scale against which the likelihood of an underspecified event can be inferred. By embedding neutral or highly likely events in the construction, we created underspecified and incongruent sentences and compared both with control sentences in which events of low expectedness were described. Imaging results showed that (i) left TPJ was activated for the underspecified sentences, and the activity in mPFC correlated with individuals' fantasizing ability and (ii) anterior cingulate cortex (ACC) was activated for the incongruent sentences, and the activity in bilateral IFG correlated with individuals' perspective taking ability. These findings suggest that brain activations in making pragmatic inference and in dealing with pragmatic failure are modulated by different components of cognitive empathy.

Neural correlates of processing passive sentences.

Previous research has shown that comprehension of complex sentences involving wh-movement (e.g., object-relative clauses) elicits activation in the left inferior frontal gyrus (IFG) and left posterior temporal cortex. However, relatively little is known about the neural correlates of processing passive sentences, which differ from other complex sentences in terms of representation (i.e., noun phrase (NP)-movement) and processing (i.e., the time course of syntactic reanalysis). In the present study, 27 adults (14 younger and 13 older) listened to passive and active sentences and performed a sentence-picture verification task using functional Magnetic Resonance Imaging (fMRI). Passive sentences, relative to active sentences, elicited greater activation in bilateral IFG and left temporo-occipital regions. Participant age did not significantly affect patterns of activation. Consistent with previous research, activation in left temporo-occipital cortex likely reflects thematic reanalysis processes, whereas, activation in the left IFG supports processing of complex syntax (i.e., NP-movement). Right IFG activation may reflect syntactic reanalysis processing demands associated with the sentence-picture verification task.

MF.04 Effects placebo of and lorazepam on emotional voice processing: An fMRI study

AimsPlacebo effects on anxiety are often observed in daily psychiatry practice, but the biological neural basis is not well understood. We investigated the effects of lorazepam and a placebo on...

Prefrontal and hippocampal contributions to the generation and binding of semantic associations during successful encoding

The ability to form and bind associations between items is an important aspect of successful memory formation. We hypothesize that, during encoding, the left inferior frontal gyrus (IFG) supports generation of associations between items and the hippocampus then binds these associations. This study examined the parametric responses of these regions to varying amounts of generative and relational processing during successful encoding (i.e., for subsequently recognized items). Encoding involved presentation of word triads varying in the number of semantic associations among them (none, one or all); participants judged how many associations were present in each triad. Thus, triads with fewer associations had higher generative load while triads with more associations had higher relational load. Participants later completed a forced-choice recognition test for encoding triads. Successful encoding relative to a control task resulted in activation of bilateral IFG and left hippocampus, and the hippocampus also exhibited a significant subsequent memory effect (hits>misses). Linear parametric analyses revealed that generative load modulated activity in bilateral IFG while relational load correlated with activity in left hippocampus. Although univariate analyses distinguished IFG and hippocampal contributions to the generative and relational stages of encoding, respectively, effective connectivity between these regions did not differ according to condition. Furthermore, this analysis revealed that the left IFG played a pivotal role in coordinating associative encoding processes. Our findings illustrate that modulation of components in a memory network can be independent of patterns of mutual connectivity among those components in mediating successful encoding.