Silence Is Golden: Transient Neural Deactivation in the Prefrontal Cortex during Attentive Reading

from Cerebral Cortex

It is becoming increasingly clear that attention-demanding tasks engage not only activation of specific cortical regions but also deactivation of other regions that could interfere with the task at hand. At the same time, electrophysiological studies in animals and humans have found that the participation of cortical regions to cognitive processes translates into local synchronization of rhythmic neural activity at frequencies above 40 Hz (so-called gamma-band synchronization). Such synchronization is seen as a potential facilitator of neural communication and synaptic plasticity. We found evidence that cognitive processes can also involve the disruption of gamma-band activity in high-order brain regions. Intracerebral electroencephalograms were recorded in 3 epileptic patients during 2 reading tasks. Visual presentation of words induced a strong deactivation in a broad (20–150 Hz) frequency range in the left ventral lateral prefrontal cortex, in parallel with gamma-band activations within the reading network, including Broca’s area. The observed energy decrease in neural signals was reproducible across patients. It peaked around 500 ms after stimulus onset and appeared subject to attention-modulated amplification. Our results suggest that cognition might be mediated by a coordinated interaction between regional gamma-band synchronizations and desynchronizations, possibly reflecting enhanced versus reduced local neural communication.

Spatiotemporal Interaction between Sound Form and Meaning during Spoken Word Perception

from Cerebral Cortex

Cortical dynamics of spoken word perception is not well understood. The possible interplay between analysis of sound form and meaning, in particular, remains elusive. We used magnetoencephalography to study cortical manifestation of phonological and semantic priming. Ten subjects listened to lists of 4 words. The first 3 words set a semantic or phonological context, and the list-final word was congruent or incongruent with this context. Attenuation of activation by priming during the first 3 words and increase of activation to semantic or phonological mismatch in the list-final word provided converging evidence: The superior temporal cortex bilaterally was involved in both analysis of sound form and meaning but the role of each hemisphere varied over time. Sensitivity to sound form was observed at 100 ms after word onset, followed by sensitivity to semantic aspects from 250 ms onwards, in the left hemisphere. From 450 ms onwards, the picture was changed, with semantic effects now present bilaterally, accompanied by a subtle late effect of sound form in the right hemisphere. Present MEG data provide a detailed spatiotemporal account of neural mechanisms during speech perception that may underlie characterizations obtained with other neuroimaging methods less sensitive in temporal or spatial domain.

The Neural Bases of the Lexical Effect: An fMRI Investigation

from Cerebral Cortex

The lexical effect is a phenomenon whereby lexical information influences the perception of the phonetic category boundary for stimuli from word–nonword continua. At issue is whether this effect is due to “top-down” influence of upper levels of processing on perceptual processing, or instead is due to decision-stage processes. In this study, brain activity was monitored using functional magnetic resonance imaging as subjects performed a phonetic categorization task on items taken from 2 continua in which one end of the continuum was a real word and the other was not (gift–kift and giss–kiss). If the lexical effect has a perceptual basis, modulation of activation should be seen as a function of the lexical effect in areas such as the superior temporal gyri (STG) which have previously been implicated in perceptual processing. In contrast, if the effect is purely due to decision-related factors, such modulation would be expected only in areas which have been linked to executive processes, such as frontal and midline structures. Modulation of activation as a function of the lexically biased shift in phonetic category boundary was observed in the STG bilaterally as well as in frontal and midline structures. This activation pattern suggests that the lexical effect has at minimum a perceptual component, in addition to an executive decision-related component. These results challenge the view that lexical effects on phonetic boundary placement are due solely to postperceptual, decision-stage processes, and support those models of language processing which allow for higher-level lexical information to directly influence the perception of incoming speech.

Time Course of Neural Activity Correlated with Colored-Hearing Synesthesia

from Cerebral Cortex

Synesthesia is defined as the involuntary and automatic perception of a stimulus in 2 or more sensory modalities (i.e., cross-modal linkage). Colored-hearing synesthetes experience colors when hearing tones or spoken utterances. Based on event-related potentials we employed electric brain tomography with high temporal resolution in colored-hearing synesthetes and nonsynesthetic controls during auditory verbal stimulation. The auditory-evoked potentials to words and letters were different between synesthetes and controls at the N1 and P2 components, showing longer latencies and lower amplitudes in synesthetes. The intracerebral sources of these components were estimated with low-resolution brain electromagnetic tomography and revealed stronger activation in synesthetes in left posterior inferior temporal regions, within the color area in the fusiform gyrus (V4), and in orbitofrontal brain regions (ventromedial and lateral). The differences occurred as early as 122 ms after stimulus onset. Our findings replicate and extend earlier reports with functional magnetic resonance imaging and positron emission tomography in colored-hearing synesthesia and contribute new information on the time course in synesthesia demonstrating the fast and possibly automatic processing of this unusual and remarkable phenomenon.

Alexia and agraphia: Contrasting perspectives of J.-M. Charcot and J. Hughlings Jackson

from Neurology

Objective: To evaluate 19th-century concepts of cerebral localization for complex mental activities, focusing on alexia and agraphia in published writings of Jean-Martin Charcot (1825–1893) and John Hughlings Jackson (1835–1911).

Background: In the early 1860s, Broca’s reports on a special role for the left frontal lobe in articulate language ignited frenetic interest in cerebral localization. Disorders of written language (alexia and agraphia) were enmeshed in ensuing discussions of how the brain was organized for language and other complex behaviors.

Design/Methods: Focused review and analysis of Charcot’s and Hughlings Jackson’s publications on aphasia, alexia, and agraphia.

Results: In the wake of Broca’s observations, the extent to which language functions in general—or such specialized functions as reading and writing—might involve focal cerebral representation was controversial. Based on his clinical–pathologic approach to “regional diagnosis,” Charcot came to value insights provided by “partial isolated aphasias.” He described patients with isolated alexia and agraphia, and he proposed a functional–anatomic framework to accommodate these disorders. Adopting a hierarchical model of nervous system organization, Hughlings Jackson argued that reading and writing could not be dissociated from other aspects of “intellectual language.” Charcot’s reductionism was typical of his era, but Hughlings Jackson’s more holistic approach was to gain ascendancy in early decades of the 20th century.

Conclusions: Charcot’s and Hughlings Jackson’s positions on alexia and agraphia reflected contrasting philosophical approaches to the study of brain disorders. Their views informed the opinions of their contemporaries and neurologic heirs in important debates on cerebral organization.

Montreal researchers warn about over-the-counter eardrops for wax buildup

from Medbroadcast.com

Researchers who studied over-the-counter eardrops for softening wax buildup are warning about the possibility of hearing loss and other problems if the drops are used by someone with a perforated eardrum.

The effect of vestibular rehabilitation supplemented by training of the breathing rhythm or proprioception exercises, in patients with chronic peripheral vestibular disease

from the Journal of Vestibular Research

Objective: To assess the effect of performing vestibular rehabilitation using the Cawthorne & Cooksey exercises supplemented by training of the breathing rhythm or proprioception exercises on self-reported disability and postural control, in patients with chronic, peripheral, vestibular disease.

Methods: Fifty one patients with peripheral vestibular disease and abnormal caloric test participated in the study (mean age 43 ± S.D. 9 years). They were assigned to one of 3 treatment groups: I. Cawthorne &} Cooksey exercises with training of the breathing rhythm (n=17); II. Cawthorne & Cooksey exercises with proprioception exercises (n=17) and III. Cawthorne & Cooksey exercises with no additional intervention (n=17). The Dizziness Handicap Inventory and static posturography were evaluated prior to treatment and at week 8 of follow-up.

Results: Prior to treatment, composite scores on the Dizziness Handicap Inventory and static posturography were similar in the 3 groups. After treatment, a decrease of the composite score of at least 18 points was observed more frequently in patients of the respiration group (94%), compared to the proprioception group (53%) and the Cawthorne & Cooksey group (70%) (p=0.03); while the proprioception group showed a significant decrease of oscillation during all sensory conditions of static posturography (p< 0.05).

Conclusion: The results suggest that regulation of the breathing pattern may have an influence on disability related to chronic vestibular disease, while proprioception exercises may improve postural control. However, further studies are needed to evaluate if training of the breathing rhythm could be an additional tool for vestibular rehabilitation.

Preserved Vestibular Evoked Myogenic Potentials (VEMP) in some patients with walking-induced oscillopsia due to bilateral vestibulopathy

from the Journal of Vestibular Research

Bilateral vestibulopathy, i.e. decreased peripheral vestibular function affecting both ears, is characterized by unsteadiness of gait, particularly in darkness and by motion-induced oscillopsia. We have recently seen a few patients with severely impaired semicircular canal function albeit with rather normal vestibular evoked myogenic potentials (VEMP) suggesting normal saccular function. The five young patients, mean age 27 years (range 15–45), 4 males and 1 female, had severely impaired balance in darkness and they all reported walking-induced vertical oscillopsia. Hence, these patients with incomplete vestibular lesions had symptoms that were indistinguishable from the typical patient with bilateral vestibulopathy. Further, the findings in these patients suggest that saccular function probably contributes little to prevent walking-induced vertical oscillopsia.

Assessing Speech Pattern Contrast Perception in Infants: Early Results on VRASPAC

from Otology & Neurotology

Objective: To assess perception of specific speech pattern contrasts in infants with normal hearing (NH) and infants with sensorineural hearing loss (HL).

Study Design: Prospective longitudinal and cross-sectional study.

Setting: Tertiary referral center.

Patients: Nine infants with NH and 11 infants with HL ranging from mild to profound.

Methods: Speech pattern contrast perception was evaluated in infants with NH and HL using a new behavioral test called Visual Reinforcement Assessment of the Perception of Speech Pattern Contrasts (VRASPAC). VRASPAC assesses the infant’s ability to distinguish the speech features of vowel height and place and consonant voicing, continuance, and place. Detection of a phonetic change is indicated by a conditioned head-turn response. Performance is reported as the percent confidence that responses are not random.

Results: The infants with NH attained high confidence scores for the vowel height and place contrasts used in this study. The infants with HL achieved high scores for the vowel height contrast regardless of degree of hearing loss. High scores were attained for the vowel place contrast by infants with losses less than 60 dB HL. Performance for the consonant contrasts was variable for all of the infants. Results from 1 infant assessed precochlear and postcochlear implantation indicated substantial improvement in speech pattern contrast perception with the implant.

Conclusion: Perception of speech pattern contrasts in infants, particularly for the vowel contrasts, can be evaluated with a high level of confidence using VRASPAC. Consonant contrast perception is much more variable than vowel contrast perception and requires further investigation.

Assessing Joint Attention and Symbolic Play in Children With Cochlear Implants and Multiple Disabilities: Two Case Studies

from Otology & Neurotology

Objective: The presence of disabilities in addition to deafness poses unique challenges for evaluating outcomes in young children who receive cochlear implants. We describe two cases in which measures of joint attention and symbolic play contributed to our understanding of progress in language acquisition following implantation for children with additional developmental disabilities.

Study Design: Prospective case study.

Setting: Tertiary referral center.

Patients: Case 1, identified with global developmental delays and implanted at age of 2 years 8 months; Case 2, diagnosed with autism spectrum disorder and implanted at age of 4 years 4 months.

Intervention: Cochlear implant.

Main Outcome Measure(s): Communication assessments were conducted using the Reynell Developmental Language Scales and the MacArthur-Bates Communicative Development Inventories before implantation (baseline) and at 12 months postimplant. Children were also videotaped during a 10-minute free play with their mothers (Joint Attention task) and 5-minute solitary play (Symbolic Play task) at baseline, 6 months, and 12 months postimplant. Videotapes were coded for child attention and play states.

Results: The MacArthur-Bates Communicative Development Inventories provided important information regarding both children’s emerging joint attention and symbolic play skills that are typically not assessed by direct measures of early child language. Videotaped parent-child interaction revealed qualitative differences in the nature of these children’s attention and play, which has important implications for intervention.

Conclusion: For these two children, obtaining developmental information from various sources, including precursor skills to the development of oral language, provided a more complete picture of each child than conventional clinician-elicited language assessments alone.

Abnormal Timing Delays in Auditory Brainstem Responses Evoked by Bilateral Cochlear Implant Use in Children

from Otology & Neurotology

Hypothesis: A period of unilateral implant use before bilateral implantation affects timing of brainstem processes measured by the electrically evoked auditory brainstem response (EABR).

Background: EABR latencies decrease with unilateral implant use potentially disrupting binaural timing cues important in auditory brainstem processing of bilateral input.

Methods: EABRs were evoked by electrical pulses from the left, right, and both implants simultaneously in 3 groups of children. All were initially implanted at ages younger than 3 years and had the following: 1) a long delay (>2 yr [n = 16]), 2) a short delay (<1 yr [n = 15]), or 3) no delay (n = 15) between left and right ear implantation. Responses were recorded on the first day of bilateral implant use and 3 and 9 months thereafter.

Results: Relative to responses evoked in the experienced ear, the naive ear showed prolonged latency in both the EABR peaks and the binaural difference response. After 3 and 9 months of bilateral implant use, the relative prolongation decreased in the long and short delay groups, but significant differences persisted in the former. No clear differences in latencies evoked by the left versus right implant were found at any time point in children receiving bilateral implants simultaneously.

Conclusion: Results suggest potential disruptions to binaural brainstem processing based on timing cues in children receiving a second cochlear implant after more than 2 years of unilateral implant use that persist through at least the first 9 months of bilateral implant use.

Clinical Assessment of Music Perception in Cochlear Implant Listeners

from Otology & Neurotology

Objective: Cochlear implants (CI) have provided tremendous benefit for speech recognition in quiet for patients with severe and profound hearing impairment, but implant users still have great difficulty perceiving music. The purpose of this study was to develop a test to quantify music perception by CI listeners in a clinically practical manner that could be standardized for administration at any implant center.

Study Design: Prospective convenience sample.

Setting: Hearing research center at an academic hospital.

Patients: Eight CI listeners, including 5 men and 3 women with implant experience ranging from 0.5 to 6 years, participated in this study. They represented a variety of implant devices and strategies.

Intervention: Administration of the Clinical Assessment of Music Perception test in a standardized sound field.

Main Outcome Measures: Music perception was assessed using a computerized test comprising pitch direction discrimination, melody identification, and timbre identification. The pitch subtest used a 2-alternative forced-choice adaptive procedure to determine a threshold interval for discrimination of complex pitch direction change. The melody and timbre subtests assessed recognition of 12 isochronous melodies and 8 musical instruments, respectively.

Results: Testing demonstrated a broad range of perceptual accuracy on all 3 subtests. Test duration averaged less than 45 minutes.

Conclusion: Clinical Assessment of Music Perception is an efficient computerized test that may be used to measure 3 different aspects of music perception in CI users in a standardized and clinically practical manner.

Children With Cochlear Implants Who Live in Monolingual and Bilingual Homes

from Otology & Neurotology

Objective: To determine if exposure to a second language impacts the ability of children with cochlear implants to develop spoken English skills.

Study Design: Matched-pairs comparison of postoperative speech perception and speech/language data of children from monolingual and bilingual homes with cochlear implants.

Setting: Tertiary medical facility.

Subjects: Twelve matched pairs of children with unilateral cochlear implants who reside in monolingual or in bilingual homes. Pairs were matched for age of implantation, cochlear anatomy, educational setting, and device type. All subjects received their implant before the age of 6 years.

Intervention: Subjects participated in routine speech perception and speech and language assessments at various postimplantation time intervals.

Main Outcome Measures: Matched-pairs t tests and mixed-model analyses were used to evaluate and compare scores obtained by the 2 groups on the Peabody Picture Vocabulary Test, The MacArthur-Bates Communicative Development Inventory: Words and Gestures, The Oral and Written Language Scales, The Infant-Toddler Meaningful Auditory Integration Scale, and the Student Oral Language Observation Matrix.

Results: No significant differences were found between the scores of children living in bilingual homes when compared with the scores obtained by children living in monolingual homes at any interval tested.

Conclusion: This study supports the belief that exposure to a second language at home does not impair primary language acquisition for some young children with cochlear implants. The study suggests that some children with cochlear implants can learn multiple spoken languages and that parents of such children do not need to avoid using a minority language with their child who has a cochlear implant.

Assessing the Use of Speech and Language Measures in Relation to Parental Perceptions of Development After Early Cochlear Implantation

from Otology & Neurotology

Objective: Clinicians and investigators use multiple outcome measures after early cochlear implantation (CI) to assess auditory skills, speech, and language effects. Are certain outcome measures better associated with optimal childhood development from the perspective of parents? We studied the association between several commonly used outcome instruments and a measure of parental perceptions of development to gain insight into how our clinical tests reflect parental perceptions of a child’s developmental status.

Study Design: Cross-sectional analysis.

Setting: Six academic centers.

Patients: One hundred eighty-eight deaf children (<6 yr) 1 year after CI activation enrolled in the longitudinal Childhood Development after CI study.

Main Outcome Measures: Measures of auditory skills, speech, and language. Parental perceptions of development quantified with a visual analogue scale (visual analogue scale-development).

Methods: Nonparametric and parametric regression methods were used to model the relationship between outcome measures and visual analogue scale-development scores.

Results: All outcome measures were positively associated with parental perceptions of development, but more robust associations were observed with language measures and a parent-report scale of auditory skills than with a selected measure of closed-set speech. For speech and language data, differences were observed in the trajectories of associations among younger (2-3 yr) versus older (4-5 yr) children.

Conclusion: Our results demonstrate the importance of measuring multiple outcome measures after early pediatric CI. The degree to which an outcome measure reflects childhood development as perceived by parents may be affected by the child’s age. Measures that are based on parental report and broader outcome measures focused on verbal language offer the potential for a fuller understanding of the true effectiveness of early implantation.

Babbling Complexity and Its Relationship to Speech and Language Outcomes in Children With Cochlear Implants

from Otology & Neurotology

Objective: To investigate if babbling complexity in early childhood is related to speech and language outcomes in later childhood in children with cochlear implants (CIs).

Study Design: Retrospective.

Setting: Tertiary care hospital.

Patients: Nineteen infants with CIs participated.

Intervention: Infants received multichannel CIs.

Main Outcome Measures: Infant vocal recordings were taken during pre- and post-CI visits up to 13 months post-CI. Vocalizations were measured using a scoring system that takes into account the phonetic complexity of infant vocalizations. Outcome variables included articulation and language measures collected at 4 years of age. Data were analyzed using correlational and regression analyses.

Results: For infants with at least 6 to 9 months of CI experience, the phonetic complexity of babbling is significantly correlated with receptive vocabulary, articulation abilities, and global language skills at 4 years of age.

Conclusion: The phonetic complexity of prelinguistic vocalizations is related to later speech and language outcomes in children with CIs. This information may be valuable in terms of tracking progress in pediatric CI users.