Investigating the neuronal network underlying language processing may contribute to a better understanding of how the brain masters this complex cognitive function with surprising ease and how language is acquired at a fast pace in infancy. Modern neuroimaging methods permit to visualize the evolvement and the function of the language network. The present paper focuses on a specific methodology, functional near-infrared spectroscopy (fNIRS), providing an overview over studies on auditory language processing and acquisition. The methodology detects oxygenation changes elicited by functional activation of the cerebral cortex. The main advantages for research on auditory language processing and its development during infancy are an undemanding application, the lack of instrumental noise, and its potential to simultaneously register electrophysiological responses. Also it constitutes an innovative approach for studying developmental issues in infants and children. The review will focus on studies on word and sentence processing including research in infants and adults.
from Brain and Language
The purpose of this study was to investigate whether brain activity related to the presence of stuttering can be identified with rapid functional MRI (fMRI) sequences that involved overt and covert speech processing tasks. The long-term goal is to develop sensitive fMRI approaches with developmentally appropriate tasks to identify deviant speech motor and auditory brain activity in children who stutter closer to the age at which recovery from stuttering is documented. Rapid sequences may be preferred for individuals or populations who do not tolerate long scanning sessions. In this report, we document the application of a picture naming and phoneme monitoring task in three minute fMRI sequences with adults who stutter (AWS). If relevant brain differences are found in AWS with these approaches that conform to previous reports, then these approaches can be extended to younger populations. Pairwise contrasts of brain BOLD activity between AWS and normally fluent adults indicated the AWS showed higher BOLD activity in the right inferior frontal gyrus (IFG), right temporal lobe and sensorimotor cortices during picture naming and and higher activity in the right IFG during phoneme monitoring. The right lateralized pattern of BOLD activity together with higher activity in sensorimotor cortices is consistent with previous reports, which indicates rapid fMRI sequences can be considered for investigating stuttering in younger participants.
Over the past years functional near-infrared spectroscopy (fNIRS) has substantially contributed to the understanding of language and its neural correlates. In contrast to other imaging techniques, fNIRS is well suited to study language function in healthy and psychiatric populations due to its cheap and easy application in a quiet and natural measurement setting. Its relative insensitivity for motion artifacts allows the use of overt speech tasks and the investigation of verbal conversation. The present review focuses on the numerous contributions of fNIRS to the field of language, its development, and related psychiatric disorders but also on its limitations and chances for the future.
from Brain and Language
Atypical lateralization of language predicts cerebral asymmetries in parietal gesture representations
Humans typically show left-hemisphere dominance both for language and manual gestures. If this reflects a dependence of these behaviors on a common cerebral specialization, then healthy left-handers with atypical organization of language should show a similar pattern for gesture. Consistent with this hypothesis, we report fMRI data indicating that sinistrals (5/15) with bilateral, or right-lateralized, language representations in inferior frontal cortex exhibit a similar atypical pattern in inferior parietal representations of familiar gestures.
Near infrared spectroscopy (NIRS) is optical technique with high temporal resolution and reasonably good spatial resolution, which allows non invasive measurement of the blood oxygenation of tissue. The current work is focused in assessing and correlating brain activation, connectivity and cortical lateralization of the frontal cortex in response to language-based stimuli, using NIRS. Experimental studies were performed on 15 normal right-handed adults, wherein the participants were presented with a verbal fluency task. The hemodynamic responses in the pre- and anterior frontal cortex were assessed in response to a word generation task in comparison to the baseline random jaw movement and rest conditions. The functional connectivity analysis was performed using zero-order correlations and the cortical lateralization was evaluated as well. An increase in oxy- and a decrease in deoxy-hemoglobin were observed during verbal fluency task in the frontal cortex. Unlike in the pre-frontal cortex, the hemodynamic response in the anterior frontal during verbal fluency task was not significantly different from that during random jaw movement. Bilateral activation and symmetrical connectivity was observed in the pre-frontal cortex, independent of the stimuli presented. A left cortical dominance and asymmetry connectivity was observed in the anterior frontal during the verbal fluency task. The work is focused to target the pediatric epileptic populations in the future, where understanding the brain functionality (activation, connectivity, and dominance) in response to language is essential as a part of the pre-surgical evaluation in a clinical environment.
from Brain Research
Speech perception; rapid temporal processing; and the left hemisphere: A case study of unilateral pure word deafness.
The mechanisms and functional anatomy underlying the early stages of speech perception are still not well understood. One way to investigate the cognitive and neural underpinnings of speech perception is by investigating patients with speech perception deficits but with preserved ability in other domains of language. One such case is reported here: patient NL shows highly impaired speech perception despite normal hearing ability and preserved semantic knowledge, speaking, and reading ability, and is thus classified as a case of pure word deafness (PWD). NL has a left temporoparietal lesion without right hemisphere damage and DTI imaging suggests that he has preserved cross-hemispheric connectivity, arguing against an account of PWD as a disconnection of left lateralized language areas from auditory input. Two experiments investigated whether NL’s speech perception deficit could instead result from an underlying problem with rapid temporal processing. Experiment 1 showed that NL has particular difficulty discriminating sounds that differ in terms of rapid temporal changes, be they speech or non-speech sounds. Experiment 2 employed an intensive training program designed to improve rapid temporal processing in language impaired children (Fast ForWord; Scientific Learning Corporation, Oakland, CA) and found that NL was able to improve his ability to discriminate rapid temporal differences in non-speech sounds, but not in speech sounds. Overall, these data suggest that patients with unilateral PWD may, in fact, have a deficit in (left lateralized) temporal processing ability, however they also show that a rapid temporal processing deficit is, by itself, unable to account for this patient’s speech perception deficit.
One of the main features of the attentional system is the capability to select between relevant and irrelevant information. However, irrelevant information interferes with the processing of the relevant one. Using high-field magnetic resonance imaging, we examined the interference effect of a verbal (color-word) and a spatial (arrow-position) Stroop task on the activation of cortical areas known to be dedicated to the attentional control. Behaviorally, we found costs from the irrelevant information in both tasks; in the brain, we found a common neural network of activation that mainly involved the dorsolateral prefrontal cortex and the anterior cingulate cortex. However, the neural circuits involved in the two tasks overlapped only partially, since processing of words in the color-word Stroop task showed a wider and more right-lateralized activation, while spatial processing in the arrow-position Stroop task resulted in a more restricted and left-lateralized activation.
Listening and reading comprehension of paragraph-length material are considered higher-order language skills fundamental to social and academic functioning. Using ecologically relevant language stimuli that were matched for difficulty according to developmental level, we analyze the effects of task, age, neuropsychological skills, and post-task performance on fMRI activation and hemispheric laterality. Areas of supramodal language processing are identified, with the most robust region being left-lateralized activation along the superior temporal sulcus. Functionally, this conjunction has a role in semantic and syntactic processing, leading us to refer to this conjunction as “comprehension cortex.” Different from adults, supramodal areas for children include less extensive inferior frontal gyrus but more extensive right cerebellum and right temporal pole. Broader neuroanatomical pathways are recruited for reading, reflecting the more active processing and larger set of cognitive demands needed for reading compared to listening to stories. ROI analyses reveal that reading is a less lateralized language task than listening in inferior frontal and superior temporal areas, which likely reflects the difficulty of the task as children in this study are still developing their reading skills. For listening to stories, temporal activation is stable by age four with no correlations with age, neuropsychological skills or post-task performance. In contrast, frontal activation during listening to stories occurs more often in older children, and frontal activation is positively correlated with better performance on comprehension questions, suggesting that the activation of frontal networks may reflect greater integration and depth of story processing.
from Brain and Language
Emotional processing may be abnormal in amyotrophic lateral sclerosis (ALS). Our aim was to explore functional anatomical correlates in the processing of aversive information in ALS patients. We examined the performance of nine non-demented ALS patients and 10 healthy controls on two functional MRI (fMRI) tasks, consisting of an emotional attribution task and a memory recognition task of unpleasant versus neutral stimuli. During the emotional decision task, subjects were asked to select one of three unpleasant or neutral words. During the memory task, subjects were asked to recognize words presented during the previous task. Controls showed, as expected, greater activation in the right middle frontal gyrus during selection of unpleasant than neutral words, and a greater activation mainly in right-sided cerebral areas during the emotional recognition task. Conversely, patients showed a general increase in activation of the left hemisphere, and reduced activation in right hemisphere in both emotional tasks. Such findings may suggest extra-motor neurodegeneration involving key circuits of emotions, mostly negative, commonly involved in FTD.
from the Journal of Neurology
The Effects of Intervening Interference on Working Memory for Sound Location as a Function of Inter-Comparison Interval
This study examined the effects of inter-comparison interval duration and intervening interference on auditory working memory (AWM) for auditory location. Interaural phase differences were used to produce localization cues for tonal stimuli and the difference limen for interaural phase difference (DL-IPD) specified as the equivalent angle of incidence between two sound sources was measured in five different conditions. These conditions consisted of three different inter-comparison intervals [300 ms (short), 5,000 ms (medium), and 15,000 ms (long)], the medium and long of which were presented both in the presence and absence of intervening tones. The presence of intervening stimuli within the medium and long inter-comparison intervals produced a significant increase in the DL-IPD compared to the medium and long inter-comparison intervals condition without intervening tones. The result obtained in the condition with a short inter-comparison interval was roughly equivalent to that obtained for the medium inter-comparison interval without intervening tones. These results suggest that the ability to retain information about the location of a sound within AWM decays slowly; however, the presence of intervening sounds readily disrupts the retention process. Overall, the results suggest that the temporal decay of information within AWM regarding the location of a sound from a listener’s environment is so gradual that it can be maintained in trace memory for tens of seconds in the absence of intervening acoustic signals. Conversely, the presence of intervening sounds within the retention interval may facilitate the use of context memory, even for shorter retention intervals, resulting in a less detailed, but relevant representation of the location that is resistant to further degradation.
from Hearing Research
Induced positive affect (PA) can improve verbal fluency performance, and induced negative affect (NA) can increase design fluency performance (Bartolic, Basso, Schefft, Glauser, & Titanic-Schefft, 1999). Building on this, the current study investigated associations between everyday mood states and executive functions. Participants (N = 74, mean age = 51.19 years) completed verbal and design fluency tasks and a self-report affect task. PA was associated with better verbal fluency performance, although NA was not associated with design fluency. Variations in everyday PA may be associated with cognitive performance, whereas greater shifts in NA might be needed to establish associations with executive functioning.
To what degree does the so-called ‘initial hit’ of the brain versus chronic epilepsy contribute towards the memory impairment observed in chronic temporal lobe epilepsy (TLE) patients? We examined cross-sectional comparisons of age-related regressions of verbal learning and memory in 1156 patients with chronic TLE (age range 6–68 years, mean epilepsy onset 14 ± 11 years) versus 1000 healthy control subjects (age range 6–80 years) and tested the hypothesis that deviations of age regressions (i.e. slowed rise, accelerated decline) will reveal critical phases during which epilepsy interferes with cognitive development. Patients were recruited over a 20-year period at the Department of Epileptology, University of Bonn. Healthy subjects were drawn from an updated normative population of the Verbaler Lern- und Merkfähigkeitstest, the German pendant to the Rey Auditory Verbal learning Test. A significant divergence of age regressions indicates that patients fail to build up adequate learning and memory performance during childhood and particularly during adolescence. The learning peak (i.e. crossover into decline) is seen earlier in patients (at about the age of 16–17 years) than for controls (at about the age of 23–24 years). Decline in performance with ageing in patients and controls runs in parallel, but due to the initial distance between the groups, patients reach very poor performance levels much earlier than controls. Patients with left and right TLEs performed worse in verbal memory than controls. In addition, patients with left TLE performed worse than those with right TLE. However, laterality differences were evident only in adolescent and adult patients, and not (or less so) in children and older patients. Independent of age, hippocampal sclerosis was associated with poorer performance than other pathologies. The results indicate developmental hindrance plus a negative interaction of cognitive impairment with mental ageing, rather than a progressively dementing decline in chronic TLE patients. During childhood, and even more so during the decade following puberty, the critical phases for establishing episodic memory deficits appear. This increases the risk of premature ‘dementia’ later on, even in the absence of an accelerated decline. Material specific verbal memory impairment in left TLE is a characteristic of the mature brain and seems to disappear at an older age. The findings suggest that increased attention is to be paid to the time of epilepsy onset and thereafter. Early control of epilepsy is demanded to counteract developmental hindrance and damage at a younger age.
The present study examined age differences in neural lateralization patterns during swallowing and three related tasks, using functional magnetic resonance imaging (fMRI). Ten healthy right-handed young adults (mean age = 21.7 years, SD = 2.1 years) and nine healthy elders (mean age = 70.2 years, SD = 3.9 years) were scanned in a 3-T MRI head scanner. Participants were visually cued to “prepare to swallow,” “swallow,” “tap your tongue,” and “clear your throat” in randomized order. Laterality preference for each task was examined within and between groups using region-of-interest (ROI) analyses in seven areas of the left and right primary sensorimotor and premotor cortices. Results of the within-group comparisons verified a more active role of the left premotor cortex in motor-cognitive planning of deglutition in both young and older adults and a more active role of selected areas of the right hemisphere during swallowing in young adults. Greater variability was seen during tongue tapping and throat clearing in both groups. Finally, as people age the cortical hemispheric control of swallowing seems to start becoming more symmetrical/bilateral, which may indicate neural compensatory mechanisms of the aging brain commonly seen for other motor and cognitive functions.