Robert N. Davis

Dyslexia-specific brain activation profile becomes normal following successful remedial training

Objectives To examine changes in the spatiotemporal brain activation profiles associated with successful completion of an intensive intervention program in individual dyslexic children. Methods The authors obtained magnetic source imaging scans during a pseudoword reading task from eight children (7 to 17 years old) before and after 80 hours of intensive remedial instruction. All children were initially diagnosed with dyslexia, marked by severe difficulties in word recognition and phonologic processing. Eight children who never experienced reading problems were also tested on two occasions separated by a 2-month interval. Results Before intervention, all children with dyslexia showed distinctly aberrant activation profiles featuring little or no activation of the posterior portion of the superior temporal gyrus (STGp), an area normally involved in phonologic processing, and increased activation of the corresponding right hemisphere area. After intervention that produced significant improvement in reading skills, activity in the left STGp increased by several orders of magnitude in every participant. No systematic changes were obtained in the activation profiles of the children without dyslexia as a function of time. Conclusions These findings suggest that the deficit in functional brain organization underlying dyslexia can be reversed after sufficiently intense intervention lasting as little as 2 months, and are consistent with current proposals that reading difficulties in many children represent a variation of normal development that can be altered by intensive intervention.

Cognitive intervention in Alzheimer disease: a randomized placebo-controlled study.

The efficacy of a cognitive intervention consisting of training in face-name associations, spaced retrieval, and cognitive stimulation was tested in a sample of 37 patients (16 men, 21 women) with probable Alzheimer disease (AD). Patients with AD were randomly assigned to receive either the cognitive intervention or a mock (placebo) intervention for 5 weeks. The placebo group then crossed over to receive the intervention. During the intervention, AD patients showed significant improvement in recall of personal information, face-name recall, and performance on the Verbal Series Attention Test. Improvement did not generalize to additional neuropsychologic measures of dementia severity, verbal memory, visual memory, word generation, or motor speed, or to caregiver-assessed patient quality of life. Results suggest that although face-name training, spaced retrieval, and cognitive stimulation may produce small gains in learning personal information and on a measure of attention, improvement does not generalize to overall neuropsychologic functioning or patient quality of life.

Does meta-cognitive theory enhance our understanding of pathological worry and anxiety?

Abstract This study tests several tenets of Wells’ meta-cognitive theory of Generalised Anxiety Disorder (GAD) by using the Meta-Cognitions Questionnaire (MCQ), which was designed to measure meta-cognition in GAD. The MCQ Cognitive Confidence subscale (MCQ-CC) predicted anxiety symptoms even after controlling for both trait anxiety and trait worry. In addition, the MCQ Uncontrollability and Danger (MCQ-UD) subscale had the highest correlation with a discriminant function that correctly classified 80.6% of nonanxious, nonworried-anxious, and GAD participants. Finally, participants who met GAD criteria exhibited significantly higher levels of meta-worry than nonanxious and nonworried-anxious participants, and exhibited both positive and negative beliefs about worry. These results offer additional support for Wells’ meta-cognitive theory of GAD, but also highlight some of its limitations with respect to predictive validity.

Brain activation profiles during the early stages of reading acquisition.

In the present study, we demonstrate for the first time the presence of an aberrant brain mechanism for reading in children who have just started acquiring reading skills. Children who, at the end of kindergarten, are found to be at risk for developing reading problems display markedly different activation profiles than children who have, at this stage, already mastered important prereading skills. This aberrant profile is characterized by the lack of engagement of the left-hemisphere superior temporal region, an area normally involved in converting print into sound, and an increase in activation in the corresponding right-hemisphere region. This finding is consistent with current cognitive models of reading acquisition and dyslexia, pointing to the critical role of phonologic awareness skills in learning to read. (J Child Neurol 2002;17:159-163).

Brain Mechanisms for Reading in Children With and Without Dyslexia: A Review of Studies of Normal Development and Plasticity

In this article we review our experience with the application of magnetic source imaging (MSI), the newest of the functional imaging methods, to the study of brain mechanisms for reading among children who read normally and among those with dyslexia. After giving a general description of MSI, we present evidence for reliable and valid maps of the brain mechanism for aural language comprehension as well as for reading. Next, we present data from 39 normal readers, 40 children with dyslexia, and 30 younger children at risk for developing a reading disability. These data show different brain activation maps for individual children with dyslexia and children at risk for dyslexia than for those of normal readers. Such differences most likely reflect aberrant brain organization underlying phonological decoding, rather than variables such as degree of effort. Finally, we present preliminary data demonstrating that the aberrant activation profiles of children with dyslexia may return to normative patterns as a result of a successful reading intervention that enables children to improve phonological decoding skills.

Differential brain activation patterns during perception of voice and tone onset time series: a MEG study.

Evoked magnetic fields were recorded from 18 adult volunteers using magnetoencephalography (MEG) during perception of speech stimuli (the endpoints of a voice onset time (VOT) series ranging from /ga/ to /ka/), analogous nonspeech stimuli (the endpoints of a two-tone series varying in relative tone onset time (TOT), and a set of harmonically complex tones varying in pitch. During the early time window (approximately 60 to approximately 130 ms post-stimulus onset), activation of the primary auditory cortex was bilaterally equal in strength for all three tasks. During the middle (approximately 130 to 800 ms) and late (800 to 1400 ms) time windows of the VOT task, activation of the posterior portion of the superior temporal gyrus (STGp) was greater in the left hemisphere than in the right hemisphere, in both group and individual data. These asymmetries were not evident in response to the nonspeech stimuli. Hemispheric asymmetries in a measure of neurophysiological activity in STGp, which includes the supratemporal plane and cortex inside the superior temporal sulcus, may reflect a specialization of association auditory cortex in the left hemisphere for processing speech sounds. Differences in late activation patterns potentially reflect the operation of a postperceptual process (e.g., rehearsal in working memory) that is restricted to speech stimuli.

Localization of ictal and interictal bursting epileptogenic activity in focal cortical dysplasia : agreement of magnetoencephalography and electrocorticography

Abstract Focal cortical dysplasia (FCD) is often associated with severe partial epilepsy. In such cases, interictal frequent rhythmic bursting epileptiform activity (FBREA) on both scalp electroencephalography (EEG) and electrocorticography (ECoG) is generally accepted to be identical to the ictal epileptiform activity. We used magnetoencephalography (or Magnetic Source Imaging (MSI)) to determine the epileptogenic zone in a 6-year-old patient with histopathologically proven FCD and normal magnetic resonance imaging (MRI). MSI was used to localize the sources of both ictal activity and FRBEA, which was then compared with ECoG findings. The intracranial sources of both types of activity co-localized in the left inferior frontal and superior temporal gyri. The location and extent of the epileptogenic area determined by MSI was essentially identical to that determined directly through extra-operative ECoG. In the absence of structural abnormalities detectable on MRI, the noninvasive method of MSI provided valuable information regarding the location and extent of the primary epileptogenic area. This was critical for pre-surgical planning regarding placement of intracranial electrodes and for risk-benefit evaluation. [Neurol Res 2002; 24: 525-530]

Levels of word processing and incidental memory: dissociable mechanisms in the temporal lobe.

Word recall is facilitated when deep (e.g. semantic) processing is applied during encoding. This fact raises the question of the existence of specific brain mechanisms supporting different levels of information processing that can modulate incidental memory performance. In this study we obtained spatiotemporal brain activation profiles, using magnetic source imaging, from 10 adult volunteers as they performed a shallow (phonological) processing task and a deep (semantic) processing task. When phonological analysis of the word stimuli into their constituent phonemes was required, activation was largely restricted to the posterior portion of the left superior temporal gyrus (area 22). Conversely, when access to lexical/semantic representations was required, activation was found predominantly in the left middle temporal gyrus and medial temporal cortex. The differential engagement of each mechanism during word encoding was associated with dramatic changes in subsequent incidental memory performance.

Inhibition/Switching Is not Necessarily Harder than Inhibition: An Analysis of the D-KEFS Color-Word Interference Test

The Delis-Kaplan Executive Function System (D-KEFS) Color-Word Interference Test (CWIT) was designed to improve upon the Stroop task by including an inhibition/switching trial, which was designed to be more difficult than the inhibition trial in terms of time to completion and number of errors. The D-KEFS standardization data support this view. However, in clinical practice, we have noticed that many people perform better on the inhibition/switching trial than the inhibition trial. We examined the prevalence and correlates of this atypical performance pattern on the CWIT. Patients seeking outpatient neuropsychological evaluation (n = 119) completed the CWIT as part of a larger test battery. About 57.1% of patients demonstrated an atypical pattern of performance for either completion time or errors. Patients with an atypical pattern for completion time were significantly slower at color naming and word reading than patients with a typical pattern. Patients with an atypical pattern for errors performed better on measures of learning and semantic verbal fluency than patients with a typical pattern. A majority of patients in our sample exhibited atypical performance on the CWIT, and some preliminary correlates of this pattern might aid clinical interpretation.

Multimodality functional imaging evaluation in a patient with Rasmussen's encephalitis

Rasmussens encephalitis (RE) is a cryptogenic progressive inflammatory disorder of the brain that causes severe neurological problems, including intractable focal epilepsy. In select patients, aggressive treatment using cerebral hemispherectomy may ameliorate the devastating cognitive decline that accompanies this disease, even if the epileptic focus appears broadly distributed. We present a case of histopathologically-confirmed RE evaluated using a multimodal process that explored the physical and functional aspects of the associated epilepsy. This process included magnetic resonance imaging, single photo emission computed tomography, electroencephalography, and magnetoencephalography (MEG). The findings indicate that functional brain imaging data may greatly assist the surgical treatment decision-making process in RE, especially when structural imaging fails to reveal definitive localizing information. In addition, MEG may provide insights about the cortical reorganization of somatosensory cortex following hemispherectomy.