FLAIR and magnetization transfer imaging of patients with post-treatment Lyme disease syndrome

OBJECTIVE

To determine patterns of abnormalities on cerebral MRI that may characterize subgroups of patients with post-treatment Lyme disease syndrome (PTLDS) and to help identify pathomechanisms of disease.

METHODS

The authors analyzed the distribution of cerebral lesions in a cohort of 27 patients with PTLDS. A subgroup of eight patients with PTLDS was further studied using whole-brain magnetization transfer ratio measures to identify abnormalities not seen on T2-weighted images.

RESULTS

Four patients had focal neurologic deficits, relapsing-remitting disease, and lesions in a distribution typical of MS. Twenty-three patients presented with nonfocal symptoms such as fatigue, subjective memory deficits, and mood disturbance. Twelve of these patients had normal MRI, including the more sensitive fluid-attenuated inversion recovery sequence, 10 had primarily punctate and subcortical lesions, and one patient had multiple periventricular lesions.

CONCLUSIONS

In a portion of patients with post-treatment Lyme disease syndrome, white-matter hyperintensities tend to occur in subcortical arteriolar watershed areas and are not specific. Magnetization transfer ratio analysis did not provide evidence for structural abnormalities of the brain parenchyma in patients with nonfocal disease.

The effects of frontal lobe lesions on goal achievement in the water jug task

Patients with prefrontal cortex lesions are impaired on a variety of planning and problem-solving tasks. We examined the problem-solving performance of 27 patients with focal frontal lobe damage on the Water Jug task. The Water Jug task has never been used to assess problem-solving ability in neurologically impaired patients nor in functional neuroimaging studies, despite sharing structural similarities with other tasks sensitive to prefrontal cortex function, including the Tower of Hanoi, Tower of London, and Wisconsin Card Sorting Task (WCST). Our results demonstrate that the Water Jug task invokes a unique combination of problem-solving and planning strategies, allowing a more precise identification of frontal lobe lesion patients' cognitive deficits. All participants (patients and matched controls) appear to be utilizing a hill-climbing strategy that does not require sophisticated planning; however, frontal lobe lesion patients (FLLs) struggled to make required "counterintuitive moves" not predicted by this strategy and found within both solution paths. Left and bilateral FLLs were more impaired than right FLLs. Analysis of the left hemisphere brain regions encompassed by the lesions of these patients found that poor performance was linked to left dorsolateral prefrontal cortex damage. We propose that patients with left dorsolateral prefrontal cortex lesions have difficulty making a decision requiring the conceptual comparison of nonverbal stimuli, manipulation of select representations of potential solutions, and are unable to appropriately inhibit a response in keeping with the final goal.

Divided attention deficits in patients with chronic fatigue syndrome

Chronic fatigue syndrome (CFS) patients and controls were compared on a variety of mood state, personality, and neuropsychological measures, including memory, word finding, and attentional tasks that required participants to focus, sustain, or divide their attention, or to perform a combination of these functions. CFS patients demonstrated a selective deficit on 3 measures of divided attention. Their performance on the other neuropsychological tests of intelligence, fluency, and memory was no different than that of normal controls despite their reports of generally diminished cognitive capacity. There was an inverse relation between CFS patient fatigue severity and performance on 1 of the divided attention measures. Given these findings, it is probable that CFS patients will report more cognitive difficulties in real-life situations that cause them to divide their effort or rapidly reallocate cognitive resources between 2 response channels (vision and audition).

The Word Completion Memory Test (WCMT): a new test to detect malingered memory deficits

In recent years, much research has focused on developing tests to detect malingering. A drawback of existing tests is their poor ability to detect malingerers possessing more "sophisticated" knowledge of neuropsychological deficits. The current study presents preliminary validation data on a new measure, the Word Completion Memory Test (WCMT), which is the first malingering test to utilize a sophisticated coaching methodology in its development. The WCMT was administered to control participants, memory-impaired patients, and coached simulators. The coached simulators were provided with specific information about and examples of memory deficits commonly experienced following closed head injury (CHI; e.g., anterograde vs. retrograde amnesia). They also read a detailed scenario describing the lifestyle and motivations likely experienced by CHI litigants, and then practiced their roles by taking a quiz about their deficits. Results showed that 93% of coached simulators and 100% of control and memory-impaired participants were correctly classified by the WCMT.

Randomized placebo-controlled trial of donepezil in patients with progressive supranuclear palsy

OBJECTIVE

There is no effective treatment for progressive supranuclear palsy (PSP). Because results of immunochemical and pharmacologic studies suggest that the cholinergic system may play a role in the cognitive and motor features of PSP, the authors investigated the effects of donepezil (10 mg/day), an acetylcholinesterase inhibitor, in 21 patients with PSP (mean age +/- SD; 65.7 +/- 4.7 years) by a randomized, double-blind, placebo-controlled crossover trial.

METHODS

Donepezil and placebo were administered for 6 weeks each with a 1-month washout period. Patients were evaluated before and at the end of each treatment phase. Outcome measures evaluated neuropsychiatric, global cognitive, frontal, memory, motor, and activities of daily living (ADL) status.

RESULTS

Two patients withdrew during the washout phase because of unrelated medical problems. Donepezil-induced systemic side effects were transient and generally mild. Because of worsening of motor function, three patients received 5 mg/day of donepezil. All patients achieved blood and CSF therapeutic levels of donepezil. While the patients were taking donepezil, their Double Memory Test scores improved, whereas their ADL/mobility scores significantly worsened.

CONCLUSION

The findings suggest that acetylcholinesterase inhibitors such as donepezil have at best selective, modest effects on cognition in patients with PSP. In light of its deleterious effects on ADL/mobility, donepezil is not recommended for this patient population.

Action planning in a virtual context after prefrontal cortex damage

Patients with frontal lobe lesions are known to encounter severe problems in the organisation of their behaviour in everyday life. Script generation tasks assess the subject's conceptual ability to formulate and evaluate a coherent and structured plan of action. In the present study, we investigated to what extent neuropsychological deficits observed at the conceptual level of action knowledge lead to impairments in action execution. We examined seven patients with prefrontal cortex damage and sixteen normal subjects. Subjects were first asked to verbally formulate a plan of action and then to use this knowledge for 'executing' the actions in a virtual 3-dimensional interactive apartment presented on a computer screen. The results indicated that the presence of the realistic context improved patients' performance. However, specific impairments were observed in patients in the execution condition, namely actions slips, omissions, failure in initiating actions and purposeless displacements. Moreover, an analysis of planning time showed that, differently of the patients group, normal subjects spent more time during plan execution as compared to plan generation. These results suggest that after a frontal lobe lesion a defective formulation of a routine plan might affect the execution of the corresponding course of actions.

Ventromedial prefrontal cortex lesions in humans eliminate implicit gender stereotyping

Patients with prefrontal cortex lesions and controls were administered an implicit association task (IAT) that measured the degree of association between male and female names and their stereotypical attributes of strength and weakness. They also completed three questionnaires measuring their explicit judgment regarding gender-related stereotypical attributes. There were no between-group differences on the explicit measures. On the IAT, patients with dorsolateral lesions and controls showed a strong association, whereas patients with ventromedial prefrontal cortex lesions had a significantly lower association, between the stereotypical attributes of men and women and their concepts of gender. This finding provides support for the hypothesis that patients with ventromedial prefrontal lesions have a deficit in automatically accessing certain aspects of overlearned associated social knowledge.

Frontotemporal dementia: report of a familial case

The authors describe a 49-year-old woman (R.K.) who presented with one year of progressive frontal lobe dysfunction, including signs of expressive aphasia. Signs of parkinsonism were absent until late in the clinical course. Neuropsychologic testing and neuroimaging studies are described. The patient died at age 55, after 7 years of symptoms. Family history was remarkable for a mother who died at the age of 45, after experiencing 7 years of progressive aphasia. R.K.'s brain showed asymmetric frontotemporal atrophy, which was more severe on the left side. Histopathologic analysis was remarkable for numerous tau-positive neurons with some classic-appearing Pick bodies and many ballooned neurons. Tau-positive glial cells were also present. The authors suggest that the abnormal tau aggregates are related to the symptoms experienced by affected members of this family.

PET evaluation of bilingual language compensation following early childhood brain damage

We report a positron emission tomography (PET) study in a 37-year-old, right handed, bilingual (English and American Sign Language) male with left frontal lobe damage, without evidence of language or general intellectual dysfunction. A brain MRI scan demonstrated an atrophic lesion of the left dorsolateral prefrontal, orbital, and opercular cortices extending from the frontal pole to precentral gyrus and including parts of anterior cingulate cortex, due to an probable infantile encephalitis. H(2) (15)O PET scans found evidence of increased right hemisphere activity compared to normal controls during spontaneous generation of narrative in both English and ASL. Neuropsychological data were within normal limits with the exception of visuospatial function. The results suggest the possibility that plasticity, unmasking of neural pathways, and or other adaptations of language function in the right hemisphere may have occurred, and are discussed with regard to the crowding hypothesis.

Comparison of apraxia in corticobasal degeneration and progressive supranuclear palsy

OBJECTIVE

To describe ideomotor apraxia in patients with corticobasal degeneration and those with progressive supranuclear palsy, two parkinsonian disorders that are often misdiagnosed due to the overlap in their clinical features, and to determine whether systematic apraxia testing is useful for differential diagnosis.

METHODS

Fourteen patients fulfilling National Institute of Neurological Disorders and Stroke-Society for Progressive Supranuclear Palsy clinical criteria for progressive supranuclear palsy, 13 patients fulfilling modified Lang criteria for corticobasal degeneration, and 12 normal healthy control subjects were given the Test of Oral and Limb Apraxia, which was scored according to the Florida Apraxia Battery for occurrence of various types of apraxic errors.

RESULTS

Both patients with progressive supranuclear palsy and corticobasal degeneration committed a greater number of apraxic errors than normal healthy control subjects on both transitive and intransitive tasks (p < 0.001 in both cases), but apraxia was much more severe in patients with corticobasal degeneration than progressive supranuclear palsy (p < 0.001). The index of apraxia severity, in combination with the assessment of the two key features of progressive supranuclear palsy (falls and vertical gaze palsy), correctly classified all patients.

CONCLUSIONS

Patients with corticobasal degeneration show more severe ideomotor apraxia than patients with progressive supranuclear palsy, and systematic assessment of ideomotor apraxia facilitates the differential diagnosis between patients with progressive supranuclear palsy and those with corticobasal degeneration.

Impairment of eyeblink classical conditioning in progressive supranuclear palsy

In a previous study we showed that learning in eyeblink classical conditioning (EBCC) is normal in Parkinson's disease (PD) and that the serial reaction time task (SRTT) is only marginally impaired. Since pathological lesions are more widespread in the atypical parkinsonian disorder of progressive supranuclear palsy (PSP) than in PD, we hypothesized that PSP patients may show more profound deficits in the EBCC and SRTT learning tasks. We therefore investigated EBCC with a delay and two trace paradigms, an SRTT and the California Verbal Learning Test (CVLT) in eight patients with PSP and an age-matched control group. In all EBCC paradigms, we found a significant difference between groups with no significant learning in PSP patients. In the SRTT, implicit learning may have been impaired, but verbal and manual sequence recall were only marginally impaired. Verbal memory was significantly worse in PSP patients than in the control group. Our study shows a dissociated pattern of learning abilities in PSP, where the EBCC as a measure of implicit learning is impaired, the explicit sequence detection in the SRTT is relatively preserved, and the verbal memory impaired. We hypothesize that the PSP patients' deficits in EBCC learning may be due to lesions of deep cerebellar nuclei. There may be a clinical role for EBCC in distinguishing PD and PSP patients.

Conjoint and extended neural networks for the computation of speech codes: the neural basis of selective impairment in reading words and pseudowords

The computation of speech codes (i.e. phonology) is an important aspect of word reading. Understanding the neural systems and mech- anisms underlying phonological processes provides a foundation for the investigation of language in the brain. We used high-resolution three-dimensional positron emission tomography (PET) to investigate neural systems essential for phonological processes. The burden of neural activities on the computation of speech codes was maximized by three rhyming tasks (rhyming words, pseudowords and words printed in mixed letter cases). Brain activation patterns associated with these tasks were compared with those of two baseline tasks involving visual feature detection. Results suggest strong left lateralized epicenters of neural activity in rhyming irrespective of gender. Word rhyming activated the same brain regions engaged in pseudoword rhyming, suggesting conjoint neural networks for phonological processing of words and pseudowords. However, pseudoword rhyming induced the largest change in cerebral blood flow and activated more voxels in the left posterior prefrontal regions and the left inferior occipital-temporal junction. In addition, pseudoword rhyming activated the left supramarginal gyrus, which was not apparent in word rhyming. These results suggest that rhyming pseudowords requires active participation of extended neural systems and networks not observed for rhyming words. The implications of the results on theories and models of visual word reading and on selective reading dysfunctions after brain lesions are discussed.

Enhancing analogic reasoning with rTMS over the left prefrontal cortex

The authors utilized repetitive transcranial magnetic stimulation (rTMS) in 16 normal volunteers to investigate the role of the left dorsolateral prefrontal cortex (PFC) in analogic reasoning. rTMS over the left and right PFC, over the left motor cortex, and sham stimulation over the left PFC were administered during memory and analogic reasoning conditions. rTMS over the left PFC led to a significant reduction in response times only in the analogy condition without affecting accuracy. These results indicate that the left PFC is relevant for analogic reasoning and that rTMS applied to the PFC can speed up solution time.

Neural correlates of auditory-visual stimulus onset asynchrony detection

Intersensory temporal synchrony is an ubiquitous sensory attribute that has proven to be critical for binding multisensory inputs, sometimes erroneously leading to dramatic perceptual illusions. However, little is known about how the brain detects temporal synchrony between multimodal sensory inputs. We used positron emission tomography to demonstrate that detecting auditory-visual stimulus onset asynchrony activates a large-scale neural network of insular, posterior parietal, prefrontal, and cerebellar areas with the highest and task-specific activity localized to the right insula. Interregional covariance analysis further showed significant task-related functional interactions between the insula, the posterior thalamus, and superior colliculus. Based on these results and the available electrophysiological and anatomical connectivity data in animals, we propose that the insula, via its known short-latency connections with the tectal system, mediates temporally defined auditory-visual interaction at an early stage of cortical processing permitting phenomena such as the ventriloquist and the McGurk illusions.

Frontotemporal dementia with novel tau pathology and a Glu342Val tau mutation

It is unclear how tau gene mutations cause frontotemporal dementia (FTD) with parkinsonism linked to chromosome 17 (FTDP-17), but those in exon 10 (E10) or the following intron may be pathogenic by altering E10 splicing, perturbing the normal 1:1 ratio of four versus three microtubule-binding repeat tau (4R:3R tau ratio) and forming tau inclusions. We report on a 55-year old woman with frontotemporal dementia and a family history of FTDP-17 in whom we found a novel E12 (Glu342Val) tau gene mutation, prominent frontotemporal neuron loss, intracytoplasmic tau aggregates, paired helical tau filaments, increased 4R tau messenger RNA, increased 4R tau without E2 or E3 inserts, decreased 4R tau with these inserts, and a 4R:3R tau ratio greater than 1 in gray and white matter. Thus, this novel Glu342Val mutation may cause FTDP-17 by unprecedented mechanisms that alter splicing of E2, E3, and E10 to preferentially increase 4R tau without amino terminal inserts and promote aggregation of tau filaments into cytopathic inclusions.

Neural correlates of imaginal aggressive behavior assessed by positron emission tomography in healthy subjects

OBJECTIVE

Neurodegenerative or traumatic lesions of the frontal lobes often lead to abnormally aggressive behavior. The authors hypothesized that the imaginal evoking of scenarios involving aggressive behavior would be associated with a modulation of the functional activity in the human frontal cortex.

METHOD

Regional cerebral blood flow (rCBF) determinations by positron emission tomography and psychophysiological measures of emotional responsivity were obtained in a group of 15 young healthy volunteers with good visual imagery abilities and no history of abnormal behavior while they imagined the same scenario with four variations involving emotionally neutral behavior and aggressive behavior.

RESULTS

Compared to the imagined neutral scenario, the imagined scenarios involving aggressive behavior were associated with significant emotional reactivity and rCBF reductions in the ventromedial prefrontal cortex, suggesting that a functional deactivation of this cortical area occurs when individuals respond to the eliciting of imagined aggressive behavior.

CONCLUSIONS

These results in healthy subjects further expand previous findings from animal and human studies by providing an in vivo functional demonstration of the involvement of the orbitofrontal cortex in the expression of aggressive behavior. They are also consistent with the hypothesis that a functional alteration of this cortical region may be present in individuals with pathological aggressive behavior.

Conceptualizing functional neuroplasticity

There are at least four major forms of functional neuroplasticity that can be studied in humans: homologous area adaptation, cross-modal reassignment, map expansion, and compensatory masquerade. Homologous area adaptation is the assumption of a particular cognitive process by a homologous region in the opposite hemisphere. Cross-modal reassignment occurs when structures previously devoted to processing a particular kind of sensory input now accepts input from a new sensory method. Map expansion is the enlargement of a functional brain region on the basis of performance. Compensatory masquerade is a novel allocation of a particular cognitive process to perform a task. By focusing on these four forms of functional neuroplasticity, several fundamental questions about how functional cooperation between brain regions is achieved can be addressed.

Dissociating the role of the medial and lateral anterior prefrontal cortex in human planning

The anterior prefrontal cortex is known to subserve higher cognitive functions such as task management and planning. Less is known, however, about the functional specialization of this cortical region in humans. Using functional MRI, we report a double dissociation: the medial anterior prefrontal cortex, in association with the ventral striatum, was engaged preferentially when subjects executed tasks in sequences that were expected, whereas the polar prefrontal cortex, in association with the dorsolateral striatum, was involved preferentially when subjects performed tasks in sequences that were contingent on unpredictable events. These results parallel the functional segregation previously described between the medial and lateral premotor cortex underlying planned and contingent motor control and extend this division to the anterior prefrontal cortex, when task management and planning are required. Thus, our findings support the assumption that common frontal organizational principles underlie motor and higher executive functions in humans.

Differential amygdala responses to winning and losing: a functional magnetic resonance imaging study in humans

The amygdala has been shown to respond to many distinct types of affective stimuli, including reward and punishment feedback in animals. In humans, winning and losing situations can be considered as reward and punishment experiences, respectively. In this study, we used functional magnetic resonance imaging (fMRI) to measure regional brain activity when human subjects were given feedback on their performance during a simple response time task in a fictitious competitive tournament. Lexical stimuli were used to convey positive 'win' or negative 'lose' feedback. The frequency of positive and negative trials was parametrically varied by the experimenters independently from the subjects' actual performance and unbeknownst to them. The results showed that the parametric increase of winning was associated with left amygdala activation whereas the parametric increase of losing was associated with right amygdala activation. These findings provide functional evidence that the human amygdala differentially responds to changes in magnitude of positive or negative reinforcement conveyed by lexical stimuli.

Toward neuroanatomical models of analogy: a positron emission tomography study of analogical mapping

Several brain regions associated with analogical mapping were identified using (15)O-positron emission tomography with 12 normal, high intelligence adults. Each trial presented during scanning consisted of a source picture of colored geometric shapes, a brief delay, and a target picture of colored geometric shapes. Analogous pictures did not share similar geometric shapes but did share the same system of abstract visuospatial relations. Participants judged whether each source-target pairing was analogous (analogy condition) or identical (literal condition). The results of the analogy-literal comparison showed activation in the dorsomedial frontal cortex and in the left hemisphere; the inferior, middle, and medial frontal cortices; the parietal cortex; and the superior occipital cortex. Based on these results as well as evidence from relevant cognitive neuroscience studies of reasoning and of executive working memory, we hypothesize that analogical mapping is mediated by the left prefrontal and inferior parietal cortices.

Planning impairments in frontal lobe dementia and frontal lobe lesion patients

Patients with frontal lobe brain damage are reportedly impaired on tasks that require plan development and execution. In this study, we examined the performance of 15 patients diagnosed with frontal lobe dementia and 14 patients with focal frontal lobe lesions on the Tower of London planning task. Patients with frontal lobe dementia committed a significantly higher number of rule violations, made more moves, and demonstrated longer solution time latencies compared to their matched controls. Patients with frontal lobe lesions demonstrated significantly delayed solution times and also made more moves compared to their matched controls. Frontal lobe lesion patient performance suggests an impairment in execution-related processes, while frontal lobe dementia patients appear to be impaired in both plan development and execution. Despite these findings, the identification of a specific cognitive impairment that induces these planning problems remains elusive.