Monthly Archives: August 2009
A common mechanism in verb and noun naming deficits in Alzheimer’s patients
We tested the ability of Alzheimer’s patients and elderly controls to name living and non-living nouns, and manner and instrument verbs. Patients’ error patterns and relative performance with different categories showed evidence of graceful degradation for both nouns and verbs, with particular domain-specific impairments for living nouns and instrument verbs. Our results support feature-based, semantic representations for nouns and verbs and support the role of inter-correlated features in noun impairment, and the role of noun knowledge in instrument verb impairment.
from Brain and Language
Not all disfluencies are are equal: The effects of disfluent repetitions on language comprehension
Disfluencies can affect language comprehension, but to date, most studies have focused on disfluent pauses such as er. We investigated whether disfluent repetitions in speech have discernible effects on listeners during language comprehension, and whether repetitions affect the linguistic processing of subsequent words in speech in ways which have been previously observed with ers. We used event-related potentials (ERPs) to measure participants’ neural responses to disfluent repetitions of words relative to acoustically identical words in fluent contexts, as well as to unpredictable and predictable words that occurred immediately post-disfluency and in fluent utterances. We additionally measured participants’ recognition memories for the predictable and unpredictable words. Repetitions elicited an early onsetting relative positivity (100–400 ms post-stimulus), clearly demonstrating listeners’ sensitivity to the presence of disfluent repetitions. Unpredictable words elicited an N400 effect. Importantly, there was no evidence that this effect, thought to reflect the difficulty of semantically integrating unpredictable compared to predictable words, differed quantitatively between fluent and disfluent utterances. Furthermore there was no evidence that the memorability of words was affected by the presence of a preceding repetition. These findings contrast with previous research which demonstrated an N400 attenuation of, and an increase in memorability for, words that were preceded by an er. However, in a later (600–900 ms) time window, unpredictable words following a repetition elicited a relative positivity. Reanalysis of previous data confirmed the presence of a similar effect following an er. The effect may reflect difficulties in resuming linguistic processing following any disruption to speech.
from Brain and Language
University Of Queensland Study Finds New Treatment For Communication Disorders
UQ researchers have found certain drugs can change how the brain processes language in a finding that has implications for new treatments of communication disorders.
In the first study of its kind, functional MRI was used to study patterns of brain activity while healthy individuals performed a language task and were given Levodopa, a drug that increases levels of dopamine, a common neurotransmitter in the brain.
Dr David Copland, from UQ’s Centre for Clinical Research and School of Health and Rehabilitation Sciences and Dr Katie McMahon and Dr Greig de Zubicaray from UQ Centre for Clinical Research.
The team found the drug improved the speed of language processing in regions of the brain associated with language and through activating brain regions more commonly associated with attention.
The findings were recently published in the prestigious journal Cerebral Cortex.
“Up until now we’ve known that problems in dopamine systems, such as those seen in schizophrenia or in Parkinson’s disease, can be associated with language difficulties,” Dr Copland said.
Fragile period of childhood brain development could underlie epilepsy
BOSTON – A form of partial epilepsy associated with auditory and other sensory hallucinations has been linked to the disruption of brain development during early childhood, according to a study led by researchers at Beth Israel Deaconess Medical Center (BIDMC).
Described in today’s Advance On-line issue of Nature Medicine, these new findings provide the first genetic link between childhood brain development and a seizure disorder that lasts throughout adulthood, and also identify a new pathway that controls how neuron circuits are “pruned” and matured.
“During early childhood – roughly between the ages of one and five – the brain undergoes a period of major circuit remodeling,” explains senior author Matthew Anderson, MD, PhD, a principal investigator in the Departments of Neurology and Pathology at BIDMC. “Our discovery that a familial form of temporal lobe epilepsy can develop at this point demonstrates the fragility of the brain during this critical period.”
The new findings focus on the development of synapses, the connections between brain cells.
“At birth, the brain is loaded with excitatory synapses which help make nerve cells ‘fire,’” explains Anderson, who is also an Assistant Professor of Neurology and Pathology at Harvard Medical School. “However, if these excess synapses are not adequately ‘pruned,’ they can overgrow, leading to excessive transmission of excitatory signals and the development of pathological conditions, including learning disabilities and autism in addition to epilepsy.”
Using a genetically engineered mouse model created in his laboratory, together with brain slice patch-clamp electrophysiology techniques, Anderson and his scientific team found that a mutant form of the LGI1 (leucine-rich glioma-inactivated 1) gene was preventing the normal brain development.
“The first clue was our discovery that LGI1 is not expressed until the exact time when excitatory synapses are matured,” said Anderson. “We subsequently learned that the mLGI1 gene was indeed prohibiting excitatory synapses from being adequately pruned, leading to an increased excitability of circuits in the brain which left it prone to excessive synchronous discharges that are characteristic of epilepsy.”
Autosomal dominant lateral temporal lobe epilepsy (ADLTE) is characterized by frequent partial seizures (two to five per month) that are associated with auditory or other sensory auras. Tonic-clonic seizures also occur in the majority of ADLTE patients, but are infrequent, developing only about once a year.
“These partial seizures can have a significant impact on a patient’s quality of life,” notes Anderson. “Because patients can be disoriented and excessively tired following a seizure event, their day-to-day lives can sometimes be seriously disrupted. And when it comes to driving and other activities, there is still a real danger associated with this condition.
“One important reason to identify genetic causes of epilepsy is the hope that these discoveries will eventually lead to new therapies,” he adds. “By identifying this new pathway, we may have found a new target for future drug development.”
from EurekAlert.org
Not all disfluencies are are equal: The effects of disfluent repetitions on language comprehension
Disfluencies can affect language comprehension, but to date, most studies have focused on disfluent pauses such as er. We investigated whether disfluent repetitions in speech have discernible effects on listeners during language comprehension, and whether repetitions affect the linguistic processing of subsequent words in speech in ways which have been previously observed with ers. We used event-related potentials (ERPs) to measure participants’ neural responses to disfluent repetitions of words relative to acoustically identical words in fluent contexts, as well as to unpredictable and predictable words that occurred immediately post-disfluency and in fluent utterances. We additionally measured participants’ recognition memories for the predictable and unpredictable words. Repetitions elicited an early onsetting relative positivity (100–400 ms post-stimulus), clearly demonstrating listeners’ sensitivity to the presence of disfluent repetitions. Unpredictable words elicited an N400 effect. Importantly, there was no evidence that this effect, thought to reflect the difficulty of semantically integrating unpredictable compared to predictable words, differed quantitatively between fluent and disfluent utterances. Furthermore there was no evidence that the memorability of words was affected by the presence of a preceding repetition. These findings contrast with previous research which demonstrated an N400 attenuation of, and an increase in memorability for, words that were preceded by an er. However, in a later (600–900 ms) time window, unpredictable words following a repetition elicited a relative positivity. Reanalysis of previous data confirmed the presence of a similar effect following an er. The effect may reflect difficulties in resuming linguistic processing following any disruption to speech.
from Brain and Language
Neuroimaging of the Functional and Structural Networks Underlying Visuospatial versus Linguistic Reasoning in High-Functioning Autism
High-functioning individuals with autism have been found to favor visuospatial processing in the face of typically poor language abilities. We aimed to examine the neurobiological basis of this difference using functional magnetic resonance imaging and diffusion tensor imaging. We compared 12 children with high functioning autism (HFA) to 12 age- and IQ-matched typically developing controls (CTRL) on a pictorial reasoning paradigm under three conditions: V, requiring visuospatial processing, S, requiring language (i.e. semantic) processing, and V + S, a hybrid condition in which language use could facilitate visuospatial transformations. Activated areas in the brain were chosen as endpoints for probabilistic diffusion tractography to examine tract integrity (FA) within the structural network underlying the activation patterns. The two groups showed similar networks, with linguistic processing activating inferior frontal, superior and middle temporal, ventral visual, and temporo-parietal areas, whereas visuospatial processing activated occipital and inferior parietal cortices. However, HFA appeared to activate occipito-parietal and ventral temporal areas, whereas CTRL relied more on frontal and temporal language regions. The increased reliance on visuospatial abilities in HFA was supported by intact connections between the inferior parietal and the ventral temporal ROIs. In contrast, the inferior frontal region showed reduced connectivity to ventral temporal and middle temporal areas in this group, reflecting impaired activation of frontal language areas in autism. The HFA group’s engagement of posterior brain regions along with its weak connections to frontal language areas suggest support for a reliance on visual mediation in autism, even in tasks of higher cognition.
from Neuropsychologia
The Split Fovea Theory and the Leicester Critique: What do the Data Say?
According to the Split Fovea Theory (SFT) recognition of foveally presented words involves interhemispheric transfer. This is because letters to the left of the fixation location are initially sent to the right hemisphere, whereas letters to the right of the fixation position are projected to the left hemisphere. Both sources of information must be integrated for words to be recognized. Evidence for the SFT comes from the Optimal Viewing Position (OVP) paradigm, in which foveal word recognition is examined as a function of the letter fixated. OVP curves are different for left and right language dominant participants, indicating a time cost when information is presented in the halffield ipsilateral to the dominant hemisphere (Hunter, Brysbaert, & Knecht, 2007). The methodology of the SFT research has recently been questioned, because not enough efforts were made to ensure adequate fixation. The aim of the present study is to test the validity of this argument. Experiment 1 replicated the OVP effect in a naming task by presenting words at different fixation positions, with the experimental settings applied in previous OVP research. Experiment 2 monitored and controlled eye fixations of the participants and presented the stimuli within the boundaries of the fovea. Exactly the same OVP curve was obtained. In Experiment 3, the eyes were also tracked and monocular viewing was used. Results again revealed the same OVP effect, although latencies were remarkably higher than in the previous experiments. From these results we can conclude that although noise is present in classical SFT studies without eye-tracking, this does not change the OVP effect observed with left dominant individuals.
from Neuropsychologia
Lexicality drives audio-motor transformations in Broca’s area
Broca’s area is classically associated with speech production. Recently, Broca’s area has also been implicated in speech perception and non-linguistic information processing. With respect to the latter function, Broca’s area is considered to be a central area in a network constituting the human mirror system, which maps observed or heard actions onto motor programs to execute analogous actions. These mechanisms share some similarities with Liberman’s motor theory, where objects of speech perception correspond to listener’s intended articulatory gestures. The aim of the current series of behavioral, TMS and fMRI studies was to test if Broca’s area is indeed implicated in such audio-motor transformations. More specifically, using a classical phonological rhyme priming paradigm, we investigated whether the role of Broca’s area could be purely phonological or rather, is lexical in nature. In the behavioral baseline study, we found a large priming effect in word prime/target pairs (W–W) and no effect for pseudo-words (PW–PW). Online TMS interference of Broca’s area canceled the priming difference between W–W and PW–PW by enhancing the effects for PW–PW. Finally, the fMRI study showed activation of Broca’s area for W–W pairs, but not for PW–PW pairs. Our data show that Broca’s area plays a significant role in speech perception strongly linked to the lexicality of a stimulus.
from Brain and Language
Rate perception and the auditory 40-Hz steady-state fields evoked by two-tone sequences
The rate perception of tone sequences reflects the physical repetition rate for identical sound elements. More complex sequences are perceived at the physical rate or at lower rates, depending on perceptual organization. Here, we used magnetoencephalography and psychophysical studies to evaluate the possible relationship between rate perception of such rapid, 40-Hz tone trains and the 40-Hz steady-state response (SSR) in human primary auditory cortex. In Experiment 1, the 40-Hz SSR evoked by monotone sequences of 1000 and 600 Hz were compared to the response evoked by alternating-tone sequences of the same frequencies. The results showed that the 40-Hz SSR for the alternating-tones was attenuated compared to the monotones. In Experiment 2, frequency differences across a range of 25 – 300 Hz were studied. Compared to a 1000-Hz monotone sequence, the 40-Hz SSR was reduced. Amplitude reduction was most prominent for frequency differences of 200 Hz and more, which were generally perceived with half-the-physical rate. We discuss possible physiological mechanisms of this finding and its relationship to perception.
from Hearing Research
A Preliminary Evaluation of Fast-ForWord-Language as an Adjuvant Treatment in Language Intervention
Rationale: Fast ForWord-Language (FFW-L) is designed to enhance children’s processing of auditory-verbal signals, and thus, their ability to learn language. As a preliminary evaluation of this claim, we examined the effects of a 5-week course of FFW-L as an adjuvant treatment with a subsequent 5-week conventional narrative based language intervention (NBLI) that targeted narrative comprehension and production and grammatical output.
Method: Twenty-three, 6- to 8-year-old children with language impairments were assigned randomly to one of three intervention sequences: (1) FFW-L/NBLI; (2) NBLI/FFW-L; and (3) Wait/NBLI. We predicted that after both treatment periods, the FFW-L/NBLI group would show greater gains on measures of narrative ability, conversational grammar, and nonword repetition than either other group.
Results: After the first 5-week study period, the intervention groups, taken together (i.e., FFWL/NBLI and NBLI/FFW-L), significantly outperformed the no treatment Wait/NBLI group on two narrative measures. At the final test period, all three groups displayed significant time-related effects on measures of narrative ability, but there were no statistically significant between-group effects of intervention sequence.
Conclusions: This preliminary study provides no evidence to support the claim that FFW-L enhances children’s response to a conventional language intervention.
Evidence for Adverse Phonatory Change Following an Inhaled Combination Treatment
Purpose: Voice problems are reportedly a frequent side-effect of inhaled combination (IC) treatments. The purpose of this experimental study was to investigate whether IC treatments are detrimental to phonation. We hypothesized that IC but not sham treatment would significantly increase phonation threshold pressure (PTP) and perceived phonatory effort (PPE).
Methods: Fourteen healthy adults participated in a repeated-measures design over two experimental days where they received IC and sham treatments in counterbalanced order. PTP and PPE were collected prior to, and immediately, 1-hour, and 2-hours following IC and sham treatment.
Results: IC but not sham treatment increased PTP. The increase in PTP was maintained for 2-hours following administration. PPE ratings were not significantly correlated with PTP.
Conclusions: IC treatments can have acute, adverse effects on phonation. Detrimental phonatory effects were elicited in participants with no self-reported voice problems. IC treatments are being increasingly prescribed across the lifespan. The current data increase our understanding of the nature of phonatory deterioration associated with IC treatment, and lay the groundwork for increased research effort to develop IC treatments that effectively control respiratory disease while minimizing an effect on phonation.
Measurement of Speech Effort During Fluency-Inducing Conditions in Adults who Do and Do Not Stutter
Purpose: To investigate the effects of four fluency-inducing (FI) conditions on self-rated speech effort and other variables in adults who stutter and in normally fluent controls.
Method: Twelve adults with persistent stuttering and 12 adults who had never stuttered each completed 4 ABA-format experiments. During A phases participants read aloud normally. During each B phase they read aloud in one of four FI conditions: auditory masking, chorus reading, whispering, and rhythmic speech. Dependent variables included self-judged speech effort and observer-judged stuttering frequency, speech rate, and speech naturalness.
Results: For the persons who stuttered, FI conditions reduced stuttering and speech effort, but only for chorus reading were these improvements obtained without diminishing speech naturalness or speaking rate. By contrast, speech effort increased during all FI conditions for adults who did not stutter.
Conclusions: Self-rated speech effort differentiated the effects of four FI conditions on speech performance for adults who stuttered, with chorus reading best approximating normally fluent speech. More generally, self-ratings of speech effort appeared to constitute an independent, reliable, and validly interpretable dimension of fluency that may be useful in the measurement and treatment of stuttering.
Producing American-English Vowels during Vocal Tract Growth: A Perceptual Categorization Study of Synthesized Vowels
Purpose: To consider interactions of vocal tract change with growth and perceived output patterns across development, the influence of non-uniform vocal tract growth on the ability to reach acoustic-perceptual targets for English vowels was studied.
Method: Thirty-seven American-English speakers participated in a perceptual categorization experiment. For the experiment, an articulatory-to-acoustic model was used to synthesize 342 five-formant vowels, covering maximal vowel spaces for speakers at five growth stages (from 6 months old to adult).
Results: Results indicate that the three vowels /i u æ/ can be correctly perceived by adult listeners when produced by speakers with a 6-month-old vocal tract. Articulatory-to-acoustic relationships for these three vowels differ across growth stages. For a given perceived vowel category, the infant tongue position is more fronted than the adult’s. Furthermore, non-uniform vocal tract growth influences degree of interarticulator coupling for a given perceived vowel, leading to a reduced correlation between jaw height and tongue body position in infant-like compared to adult vocal tracts.
Conclusion: Findings suggest that non-uniform vocal tract growth does not prevent the speaker from producing acoustic-auditory targets related to American-English vowels. However, the relationships between articulatory configurations and perceptual targets change from birth to adulthood.
