Left Frontal Lobe Regions Research Articles

Brain activation patterns in patients with post-stroke cognitive impairment during working memory task: a functional near-infrared spectroscopy study.

To explore the activation patterns in the frontal cortex of patients with post-stroke cognitive impairment during the execution of working memory tasks. 15 patients with post-stroke cognitive impairment, 17 patients without cognitive impairment, and 15 healthy controls of similar age and sex were included. All participants under-went immediate recall task testing and near-infrared spectroscopy imaging to measure frontal cortex activation during the task. The healthy control group performed the best in the immediate recall task, followed by the post-stroke non-cognitive impairment group. The post-stroke cognitive impairment group had the poorest performance. The near-infrared spectroscopy results revealed that during the immediate recall task, the healthy control group primarily activated the left frontal lobe region. In contrast, post-stroke patients exhibited reduced activation in the left frontal lobe and increased activation in the right frontal cortex, particularly in the right frontopolar and orbitofrontal regions, with the post-stroke cognitive impairment group displaying the most pronounced changes. Patients with post-stroke cognitive impairment exhibit reduced activation in the left prefrontal cortex during the working memory tasks. They rely on compensatory activation in the right prefrontal cortex, particularly in the frontopolar and orbitofrontal cortex, to successfully complete the task.

Dysembryoplastic Neuroepithelial Tumor (Dnet) in a Young Female: A Rare Case Presentation

Dysembryoplastic neuroepithelial tumor (DNET) is a recently described, morphologically unique, and surgically curable low grade brain tumor which is included in the WHO CNS classification as neuronal and mixed neuronal glial tumor. It is usually seen in children and young adults. This entity first described by Damas-Duport in 1998 is usually non-recurring with an excellent prognosis. We present a case of 30 year old female experiencing seizures with well defined space occupying lesion in the frontal region of brain. Contrast enhanced Magnetic Resonance Imaging was done which revealed well defined multilobulated solid cystic mass lesion in cortical/ subcortical region of left frontal lobe. Histological features suggested dysembryoplastic neuroepithelial tumor which was subsequently confirmed on immunohistochemistry by GFAP and S-100 positivity. The principal differential diagnosis is oligodendrogliomas and gangliogliomas. Patient did not receive any adjuvant therapy post operatively and showed no signs of residual disease or recurrence on magnetic resonance imaging during follow up. Patient is on phenytoin for prophylaxis of seizures.

A functional dissociation of the left frontal regions that contribute to single word production tasks

Controversy surrounds the interpretation of higher activation for pseudoword compared to word reading in the left precentral gyrus and pars opercularis. Specifically, does activation in these regions reflect: (1) the demands on sublexical assembly of articulatory codes, or (2) retrieval effort because the combinations of articulatory codes are unfamiliar? Using fMRI, in 84 neurologically intact participants, we addressed this issue by comparing reading and repetition of words (W) and pseudowords (P) to naming objects (O) from pictures or sounds. As objects do not provide sublexical articulatory cues, we hypothesis that retrieval effort will be greater for object naming than word repetition/reading (which benefits from both lexical and sublexical cues); while the demands on sublexical assembly will be higher for pseudoword production than object naming.We found that activation was: (i) highest for pseudoword reading [P>O&W in the visual modality] in the anterior part of the ventral precentral gyrus bordering the precentral sulcus (vPCg/vPCs), consistent with the sublexical assembly of articulatory codes; but (ii) as high for object naming as pseudoword production [P&O>W] in dorsal precentral gyrus (dPCg) and the left inferior frontal junction (IFJ), consistent with retrieval demands and cognitive control.In addition, we dissociate the response properties of vPCg/vPCs, dPCg and IFJ from other left frontal lobe regions that are activated during single word speech production. Specifically, in both auditory and visual modalities: a central part of vPCg (head and face area) was more activated for verbal than nonverbal stimuli [P&W>O]; and the pars orbitalis and inferior frontal sulcus were most activated during object naming [O>W&P]. Our findings help to resolve a previous discrepancy in the literature, dissociate three functionally distinct parts of the precentral gyrus, and refine our knowledge of the functional anatomy of speech production in the left frontal lobe.

Morphological processing in Chinese engages left temporal regions

Morphological awareness, the ability to manipulate the smallest units of meaning, is critical for Chinese literacy. This is because Chinese characters typically reflect the morphemic, or morpho-syllabic units of language. Yet, the neurocognitive mechanisms underlying Chinese speakers’ morphological processing remain understudied. Proficient readers (N = 14) completed morphological and phonological judgment tasks in Chinese, in both auditory and visual modalities, during fMRI imaging. Key to our inquiry were patterns of activation in left temporal regions, especially the superior temporal gyrus, which is critical for phonological processing and reading success. The findings revealed that morphological tasks elicited robust activation in superior and middle temporal regions commonly associated with automated phonological and lexico-semantic analyses. In contrast, the rhyme judgment task elicited greater activation in left frontal lobe regions, reflecting the analytical complexity of sound-to-print mapping in Chinese. The findings suggest that left temporal regions are sensitive to salient morpho-syllabic characteristics of a given language.

Changes in brain FDG metabolism induced by acupuncture in healthy volunteers

With the aid of newly developed functional brain imaging studies, studies are ongoing to see if acupuncture first acts on specific brain areas to induce effects on the human body. To examine if stimulation at specific acupuncture points changes brain glucose metabolism patterns, including the limbic system and specific brain areas related to the acupuncture effect in healthy volunteers using fluorodeoxyglucose positron emission tomography combined computed tomography (FDG-PET/CT). Twenty healthy volunteers (11 men and 9 women; mean age 49.1+/-7.3 years, age range 35-62 years) were included. Two sets of PET/CT scans were obtained from each volunteer, with and without stimulation by acupuncture. Two classic acupoints, LR3 (liver meridian) and ST44 (stomach meridian) were tested at the same time, using disposable sterile stainless steel needles. After initial acupuncture, the needle was kept in place without further stimulation. FDG-PET/CT scan of the brain began 45 min after FDG injection (185-222 MBq). After stimulation of LR3 and ST44 by acupuncture, glucose metabolism in the brain was increased in the left insula (BA 13), bilateral thalami, superior frontal region of the right frontal lobe, and the inferior frontal region of left frontal lobe compared with baseline. On the other hand, glucose metabolism was decreased after acupuncture in the cingulate and parahippocampal (BA 36) regions of the left limbic lobe. Changes of glucose metabolism in specific brain areas following stimulation by acupuncture on LR3 and ST44 were documented using FDG-PET/CT.

Comparative study of proton magnetic resonance spectroscopy on frontal lobe between patients with paranoid schizophrenia and patients with bipolar mania

Objective To compare biochemical characteristics of the frontal lobe tissue between patients with paranoid schizophrenia and patients with bipolar mania by using proton magnetic resonance spectroscopy （ ^1 H MRS）. Methods The ratios of N-Acetylaspartate （NAA） , choline（CHo） and myoinositol（mI） to creatine （Cr） were measured using a 3.0 T GE Signa EXCITE MR system in 25 patients with paranoid schizophrenia, 20 patients with bipolar mania and 32 healthy subjects matched for age, gender, and years of education. ANOVA and partial correlation analysis were used for statistic process. Cerebral asymmetry of frontal lobe metabolism were also analyzed. Results Patients with paranoid schizophrenia presented markedly elevated Cho/Cr in left frontal lobe regions when compared to patients with bipolar mania and normal controls （ 1.14 ± 0. 14,1.06 ± 0.08,1.04 ± 0.14, respectively, P = 0.03, P = 0.01 ） , but patients with bipolar mania showed no significant difference with normal controls （ P 〉 0.05 ）. There were no significant difference in NAA/Cr , mI/Cr for left frontal lobe regions , and NAA/Cr, Cho/Cr, mI/Cr for right frontal lobe among the groups （ all P 〉 0.05 ）. The lateralization index of NAA/ Cr, Cho/Cr in frontal lobe region in three groups had no significant difference compared with 1.0 （ all P 〉 0.05 ）. No correlation were found between metabolite and symptoms scale scores, disease course. Conclusion Elevation of Cho/Cr in left frontal lobe regions may be special to patients with paranoid schizophrenia. Key words: Schizophrenia; Bipolar disorder; Frontal lobe; Proton magnetic resonance spectroscopy

Consonant and vowel discrimination by brain-damaged individuals: effects of phonological segmentation

Two ‘same–different’ discrimination tasks were conducted to explore consonant voicing and vowel discrimination abilities in groups of left- and right-hemisphere-damaged individuals and normal controls. Stimuli were manipulated such that for half of each set, segmentation of the syllable was required for a discrimination decision; for the other half of the stimuli, no phonological segmentation was required. Results revealed impaired consonant voicing and vowel discrimination in a group of left-hemisphere-damaged non-fluent aphasic participants. Discrimination accuracy for groups of fluent aphasic participants and right-hemisphere-damaged participants fell between those of the non-fluent aphasic participants and the normal controls on both tasks. The findings are suggestive of a role for left frontal lobe regions in phonological segmentation, but remain inconclusive on this issue. The results are considered in relation to models of the neural bases and cerebral lateralization of speech perception processes.

Memory for object-features versus memory for object-location: A positron emission tomography study of encoding and retrieval processes

Abstract Regional cerebral blood flow was measured with positron-emission tomography during two encoding and two retrieval tasks that were designed to compare memory for object features with memory for object locations. Bilateral increases in regional cerebral blood flow were observed in both anterior and posterior regions of inferior temporal cortex and in ventral regions of prestriate cortex, when the condition that required retrieval of object locations was subtracted from the condition that required retrieval of object features. During encoding, these changes were less pronounced and were restricted to the left inferior temporal cortex and right ventral prestriate cortex. In contrast, both encoding and retrieval of object location were associated with bilateral changes in dorsal prestriate and posterior parietal cortex. Finally, the two encoding conditions activated left frontal lobe regions preferentially, whereas the two retrieval conditions activated right frontal lobe regions. These findings confirm that, in human subjects, memory for object features is mediated by a distributed system that includes ventral prestriate cortex and both anterior and posterior regions of the inferior temporal gyrus. In contrast, memory for the locations of objects appears to be mediated by an anatomically distinct system that includes more dorsal regions of prestriate cortex and posterior regions of the parietal lobe.