Jussi Numminen

Speaking modifies voice-evoked activity in the human auditory cortex.

The voice we most often hear is our own, and proper interaction between speaking and hearing is essential for both acquisition and performance of spoken language. Disturbed audiovocal interactions have been implicated in aphasia, stuttering, and schizophrenic voice hallucinations, but paradigms for a noninvasive assessment of auditory self‐monitoring of speaking and its possible dysfunctions are rare. Using magnetoencephalograpy we show here that self‐uttered syllables transiently activate the speakers auditory cortex around 100 ms after voice onset. These phasic responses were delayed by 11 ms in the speech‐dominant left hemisphere relative to the right, whereas during listening to a replay of the same utterances the response latencies were symmetric. Moreover, the auditory cortices did not react to rare vowel changes interspersed randomly within a series of repetitively spoken vowels, in contrast to regular change‐related responses evoked 100–200 ms after replayed rare vowels. Thus, speaking primes the human auditory cortex at a millisecond time scale, dampening and delaying reactions to self‐produced “expected” sounds, more prominently in the speech‐dominant hemisphere. Such motor‐to‐sensory priming of early auditory cortex responses during voicing constitutes one element of speech self‐monitoring that could be compromised in central speech disorders. Hum. Brain Mapping 9:183–191, 2000.

Subject's own speech reduces reactivity of the human auditory cortex

Previous studies on monkeys have shown that uttering-related cortical areas exert an inhibitory effect on the auditory cortex, and cerebral blood-flow analyses on humans have revealed modulation of the activity of the auditory cortex during own speech. To study this modulation on a millisecond time scale, we recorded neuromagnetic evoked responses to short 1-kHz tones while the subjects were reading silently and aloud. The 100-ms response (M100) of the auditory cortex was delayed by 10-21 ms and its amplitude was dampened by 44-71% during reading aloud compared with reading silently. This effect was more prominent in responses to ipsilateral than contralateral tones, possibly due to a sum effect of diminished ipsilateral input to the cortex and decreased transcallosal excitation.

Perceiving and naming actions and objects

Neuropsychological studies have suggested differences in the cortical representations of verbs and nouns. Assessment of word-class specific deficits often relies on picture naming with different sets of images used for action and object naming. Such a setup may be problematic in neuroimaging studies, as the perception of the image and the actual differences in retrieving verbs or nouns become intertwined. To address this issue, we investigated how different sets of images affect the pattern of activation in action and object naming. In the present fMRI experiment, healthy volunteers silently performed both action and object naming from action images, and object naming from object-only images. A similar network of cortical areas was activated in all three conditions, including bilateral occipitotemporal and parietal regions, and left frontal cortex. With action images, noun retrieval enhanced activation in bilateral parietal and right frontal cortex, areas previously associated with visual search and attention. Increased activation in the left posterior parietal cortex during this condition also suggests that naming an object in the context of action emphasizes motor-based properties of objects. Action images, regardless of whether verbs or nouns were named, evoked stronger activation than object-only images in the posterior middle temporal cortex bilaterally, the left temporo-parietal junction, and the left frontal cortex, a network previously identified in processing of action knowledge. The strong influence of perceptual input on neural activation associated with noun vs. verb naming can in part explain discrepancies in previous lesion and functional neuroimaging studies on the processing of nouns and verbs.

Pre- and post-operative diffusion tensor imaging of the median nerve in carpal tunnel syndrome

ObjectivesTo use pre- and post-operative diffusion tensor imaging (DTI) to monitor median nerve integrity in patients suffering from carpal tunnel syndrome (CTS).MethodsDiffusivity and anisotropy images along the median nerve were compared among 12 patients, 12 age-matched and 12 young control subjects and correlated with electrophysiological neurography results. Slice-wise DTI parameter values were calculated to focus on local changes.ResultsResults of pre-operative patients and age-matched control subjects differed only in the distal nerve. Moreover, pre-operative patients differed significantly from young controls and post-operative patients. The main abnormalities were increased diffusivity and decreased anisotropy in the carpal tunnel and distal median nerve. Post-operative clinical improvement was reflected in diffusivity, but not in anisotropy. Slice-wise analysis showed high pre-operative diffusivity at the distal nerve. All groups had relatively large inter-subject variation in both diffusivity and anisotropy.ConclusionsDTI can provide information complementary to clinical examination, electrophysiological recordings and anatomical MRI of diseases and injuries of peripheral nerves. However, similar age-related changes in diffusivity and anisotropy may weaken DTI specificity. Slice-wise analysis is necessary for detection of local changes in nerve integrity.Key Points• Diffusion tensor magnetic resonance imaging provides information complementary to conventional diagnostic methods.• Age caused similar changes to diffusivity and anisotropy as carpal tunnel syndrome.• Post-operative clinical improvement was reflected in diffusivity, but not in anisotropy.• Inter-subject variation in diffusivity and anisotropy was considerable.

De Novo and Recurrent Aneurysms in Pediatric Patients With Cerebral Aneurysms

Background and Purpose— Long-term angiographic follow-up studies on pediatric aneurysm patients are scarce. Methods— We gathered long-term clinical and angiographic follow-up data on all pediatric aneurysm patients (⩽18 years at diagnosis) treated at the Department of Neurosurgery, Helsinki University Central Hospital, between 1937 and 2009. Results— Fifty-nine patients with cerebral aneurysms in childhood had long-term clinical and radiological follow-up (median, 34 years; range, 4–56 years). Twenty-four patients (41%) were diagnosed with altogether 25 de novo and 11 recurrent aneurysms, with 9 (25%) of the aneurysms being symptomatic. New subarachnoid hemorrhage occurred in 7 patients; 4 of these patients died. Eight patients (33%) had multiple new aneurysms. The annual rate of hemorrhage was 0.4%, and the annual rate for the development of de novo or recurrent aneurysm was 1.9%. There were no de novo aneurysms in 7 patients with previously unruptured aneurysms. However, 1 recurrent aneurysm was diagnosed. Current and previous smoking (risk ratio, 2.44; 95% confidence interval, 1.07–5.55) was the only statistically significant risk factor for de novo and recurrent aneurysm formation in patients with previous subarachnoid hemorrhage, whereas hypertension, sex, or age at onset had no statistically significant effect. Smoking was also a statistically significant risk factor for new subarachnoid hemorrhage. Conclusions— Patients with ruptured intracranial aneurysms in childhood have a high risk for new aneurysms and new subarachnoid hemorrhage, especially if they start to smoke as adults. Life-long angiographic follow-up is mandatory.

Dorsal penile nerve stimulation elicits left-hemisphere dominant activation in the second somatosensory cortex

Activation of peripheral mixed and cutaneous nerves activates a distributed cortical network including the second somatosensory cortex (SII) in the parietal operculum. SII activation has not been previously reported in the stimulation of the dorsal penile nerve (DPN). We recorded somatosensory evoked fields (SEFs) to DPN stimulation from 7 healthy adults with a 122‐channel whole‐scalp neuromagnetometer. Electrical pulses were applied once every 0.5 or 1.5 sec to the left and right DPN. For comparison, left and right median and tibial nerves were stimulated alternatingly at 1.5‐sec intervals. DPN stimuli elicited weak, early responses in the vicinity of responses to tibial nerve stimulation in the primary somatosensory cortex. Strong later responses, peaking at 107–126 msec were evoked in the SII cortices of both hemispheres, with left‐hemisphere dominance. In addition to tactile processing, SII could also contribute to mediating emotional effects of DPN stimuli. Hum. Brain Mapping 18:90–99, 2003.

Strength of prefrontal activation predicts intensity of suggestion-induced pain.

Suggestion, a powerful factor in everyday social interaction, is most effective during hypnosis. Subjective evaluations and brain‐imaging findings converge to propose that hypnotic suggestion strongly modulates sensory processing. To reveal the brain regions that mediate such a modulation, we analyzed data from a functional‐magnetic‐resonance‐imaging study on hypnotic‐suggestion‐induced pain on 14 suggestible subjects. Activation strengths in the right dorsolateral prefrontal cortex (DLPFC) during initiation of suggestion for pain correlated positively with the subjective intensity of the subsequent suggestion‐induced pain, as well as with the strengths of the maximum pain‐related activation in the in the secondary somatosensory (SII) cortex. Furthermore, activation of the insula and the anterior cingulate cortex predicted the pain‐related SII activation. The right DLPFC, as an area important for executive functions, likely contributes to functional modulation in the modality‐specific target areas of given suggestions. Hum Brain Mapp 2009.

Distributions and sources of magnetoencephalographic K-complexes

Whole-head magnetoencephalographic (MEG) and midline electroencephalographic (EEG) signals were simultaneously recorded from 6 subjects during drowsiness and sleep to define the topography and source distribution of K-complexes. In light sleep, K-complexes were also triggered by infrequent tones. Distributions of spontaneous and triggered magnetic K-complexes did not differ systematically, nor did those evoked by right- and left-ear stimuli, but there were large intra- and interindividual differences. Minimum-norm estimates and current dipoles were used to characterize the source currents. Current direction and distribution varied remarkably between the K-complexes appearing in similar situations. In one subject, most K-complexes were adequately modelled with two current dipoles which were situated in the left and right inferior parietal lobes. In other subjects, the current distributions were more complex, suggesting several brain regions to be active during one K-complex; the dominant foci were in frontal and parietal lobes. Our results suggest that the K-complex is not a stereotyped response of the cortex to internal or external stimuli, comparable to evoked responses, but a diffuse and variable cortical reaction during which large areas of cortex may be active.

Cortical activation during a spatiotemporal tactile comparison task

Tactile sensory memory is needed to infer shape or motion from the spatiotemporal pattern of sensory input during manual exploration. Here we applied triplets of pressure pulses to the fingertips of subjects who were asked to respond when successive triplets were the same (COMPARE task) or when a particular stimulus was included in a triplet (CONTROL task). Stimulus sequences (30 s) alternated with rest blocks (30 s) and functional magnetic resonance images (fMRIs) were acquired in a 1.5-T scanner. During the COMPARE task, we found enhanced activation in inferior parietal cortex, supplementary motor area (SMA), and right dorsolateral prefrontal cortex (DLPFC). Activation of DLPFC is likely to be related to the attempt to memorize the stimulus sequences and activations of SMA and inferior parietal cortex to the analysis of temporospatial tactile patterns and, more generally, to guidance of haptic exploration. In addition, task-specific activation was seen in anterior cingulate gyrus, possibly related to the high mental effort required by the comparison task. Our rhythmic tactile stimulus as such, without any task-specific enhancement, activated also left cerebellum and (mainly left) putamen, supporting the idea that these structures are related to perception of temporal order of tactile stimuli.

Default Mode and Executive Networks Areas: Association with the Serial Order in Divergent Thinking.

Scientific findings have suggested a two-fold structure of the cognitive process. By using the heuristic thinking mode, people automatically process information that tends to be invariant across days, whereas by using the explicit thinking mode people explicitly process information that tends to be variant compared to typical previously learned information patterns. Previous studies on creativity found an association between creativity and the brain regions in the prefrontal cortex, the anterior cingulate cortex, the default mode network and the executive network. However, which neural networks contribute to the explicit mode of thinking during idea generation remains an open question. We employed an fMRI paradigm to examine which brain regions were activated when participants (n = 16) mentally generated alternative uses for everyday objects. Most previous creativity studies required participants to verbalize responses during idea generation, whereas in this study participants produced mental alternatives without verbalizing. This study found activation in the left anterior insula when contrasting idea generation and object identification. This finding suggests that the insula (part of the brain’s salience network) plays a role in facilitating both the central executive and default mode networks to activate idea generation. We also investigated closely the effect of the serial order of idea being generated on brain responses: The amplitude of fMRI responses correlated positively with the serial order of idea being generated in the anterior cingulate cortex, which is part of the central executive network. Positive correlation with the serial order was also observed in the regions typically assigned to the default mode network: the precuneus/cuneus, inferior parietal lobule and posterior cingulate cortex. These networks support the explicit mode of thinking and help the individual to convert conventional mental models to new ones. The serial order correlated negatively with the BOLD responses in the posterior presupplementary motor area, left premotor cortex, right cerebellum and left inferior frontal gyrus. This finding might imply that idea generation without a verbal processing demand reflecting lack of need for new object identification in idea generation events. The results of the study are consistent with recent creativity studies, which emphasize that the creativity process involves working memory capacity to spontaneously shift between different kinds of thinking modes according to the context.