Impairments of attention after cingulotomy.

BACKGROUND: Outcome studies have generally not indicated significant cognitive disturbances after cingulotomy. There is now considerable evidence that the cingulate may play an important role in emotional behavior and attention. OBJECTIVE: To characterize impairments of attention associated with bilateral lesions of the anterior cingulate cortex produced by cingulotomy. METHODS: Twelve patients who underwent cingulotomy for treatment of intractable pain were administered tests of attention, executive functions, response intention and production, and a broad range of other neurocognitive functions before surgery and again 3 and 12 months after surgery. Data from this within-subjects repeated-measures design were analyzed by multivariate analysis of variance procedures. RESULTS: After cingulotomy, patients initially had executive and attentional impairments. By 12 months, these had resolved into more circumscribed deficits, with greatest impairments on tasks requiring intention and spontaneous response production, and milder impairments of focused and sustained attention. Other aspects of attention and other cognitive functions were generally unaffected. CONCLUSION: The anterior cingulate cortex modulates response intention and focused attention.     

Progressive language disorder due to lobar atrophy.

Sixteen patients with progressive language disorder have been studied longitudinally. Anomia was a prominent presenting characteristic and mutism ultimately occurred. Patients, however, were clinically heterogeneous. Some exhibited nonfluent, agrammatic features, whereas others demonstrated a fluent aphasia, with profound loss of word meaning. Although language disorder remained the sole symptom in a minority of patients, in others an associative agnosia or personality and behavioral changes, or both, emerged. Findings on computed tomography and single photon emission tomography mirrored the areas of dysfunction suggested by the neuropsychological profiles and demonstrated abnormalities restricted to the left hemisphere or involving bilateral frontotemporal cortices. Brains of 3 patients, with distinctive clinical pictures, have been examined at autopsy. Each revealed a focal distribution of atrophy, gliosis and spongiform change, and an absence of senile plaques and neurofibrillary tangles. There was clinical and pathological overlap with frontal lobe dementia. We argue that progressive language disorder is clinically heterogeneous and forms part of a spectrum of clinical presentations of non-Alzheimer lobar atrophy.     

Transcortical sensory aphasia following a left frontal lobe infarction probably due to anomalously represented language areas

A 57-year-old right-handed man presented with speech disturbance 1 day prior to his admission. The standardized aphasia test batteries showed transcortical sensory aphasia. MRI revealed a left frontal and insular infarct. Positron emission tomography scans also revealed a glucose hypometabolism in the same region as the infarcted area on MRI. Repeated aphasia testing showed that his aphasia only partially improved.     

Unilateral spatial neglect due to right frontal lobe haematoma.

Two patients with unilateral spatial neglect caused by right frontal lobe lesions underwent cerebral blood flow studies. A 54-year-old, right-handed woman developed left hemiplegia and frontal lobe neglect associated with cerebral haemorrhage after surgical excision of a frontal tumour. A 66-year-old, right-handed woman developed a haemorrhage in the right frontal lobe caused by rupture of an aneurysm. This was followed by left hemiplegia and frontal lobe neglect. In both cases, 123I-iodoamphetamine single photon emission CT disclosed a reduction in regional cerebral blood flow localised along the circumference of the haematoma in the frontal lobe, but did not reveal any lesions in the parieto-occipital junction. These findings suggest that, in these two cases, the frontal lobe neglect was caused by lesions confined to the frontal lobe.     

Early cognitive and language skills are linked to resting frontal gamma power across the first 3 years

High-frequency cortical activity in humans and animals has been linked to a wide variety of higher cognitive processes. This research suggests that specific changes in neuronal synchrony occur during cognitive processing, distinguished by emergence of fast oscillations in the gamma frequency range. To determine whether the development of high-frequency brain oscillations can be related to the development of cognitive abilities, we studied the power spectra of resting EEG in children 16, 24 and 36 months of age. Individual differences in the distribution of frontal gamma power during rest were highly correlated with concurrent language and cognitive skills at all ages. Gamma power was also associated with attention measures; children who were observed as having better inhibitory control and more mature attention shifting abilities had higher gamma power density functions. We included a group of children with a family history of language impairment (FH+) and thus at higher risk for language disorders. FH+ children, as a group, showed consistently lower gamma over frontal regions than the well-matched FH- controls with no such family history (FH-). We suggest that the emergence of high-frequency neural synchrony may be critical for cognitive and linguistic development, and that children at risk for language impairments may lag in this process.     

Left and right basal ganglia and frontal activity during language generation: contributions to lexical, semantic, and phonological processes.

fMRI was used to determine the frontal, basal ganglia, and thalamic structures engaged by three facets of language generation: lexical status of generated items, the use of semantic vs. phonological information during language generation, and rate of generation. During fMRI, 21 neurologically normal subjects performed four tasks: generation of nonsense syllables given beginning and ending consonant blends, generation of words given a rhyming word, generation of words given a semantic category at a fast rate (matched to the rate of nonsense syllable generation), and generation of words given a semantic category at a slow rate (matched to the rate of generating of rhyming words). Components of a left pre-SMA-dorsal caudate nucleus-ventral anterior thalamic loop were active during word generation from rhyming or category cues but not during nonsense syllable generation. Findings indicate that this loop is involved in retrieving words from pre-existing lexical stores. Relatively diffuse activity in the right basal ganglia (caudate nucleus and putamen) also was found during word-generation tasks but not during nonsense syllable generation. Given the relative absence of right frontal activity during the word generation tasks, we suggest that the right basal ganglia activity serves to suppress right frontal activity, preventing right frontal structures from interfering with language production. Current findings establish roles for the left and the right basal ganglia in word generation. Hypotheses are discussed for future research to help refine our understanding of basal ganglia functions in language generation.     

A review of rating scales for measuring behavior change due to frontal systems damage.

OBJECTIVE: To perform a critical review of scales designed to measure frontal behavior change. BACKGROUND: Changes in cognition due to frontal disease or damage have been well described, but noncognitive changes in behavior are often more deleterious functionally for frontal patients. METHOD: The review concentrates on five behavior rating scales: the Behavior Rating Inventory of Executive Functions (BRIEF), the Dysexecutive Questionnaire (DEX), the Frontal Behavior Inventory (FBI), the Frontal Systems Behavior Scale (FrSBe), the Iowa Rating Scales of Personality Change (IRSPC), and the Neuropsychiatric Inventory (NPI). Other scales purporting to measure specific aspects of frontal functioning, but having less research support, are described briefly. RESULTS AND CONCLUSIONS: The BRIEF and FrSBe have good reliability and large-scale norms. No norms are available for the other scales. The FrSBe and IRSPC have been shown to be valid in discriminating frontal from nonfrontal lesioned patients, but this has not been shown in the other scales. The FBI and NPI require trained raters, whereas the FrSBe, IRSPC, and BRIEF are administered to patients and/or family informants directly. The NPI and FBI are sensitive to certain changes in behavior attributed to frontal systems disruption but have been used primarily in dementia.     

Decreased energy demanding processes in the frontal lobes of schizophrenics due to neuroleptics? A P-magneto-resonance spectroscopic study

In the present investigation on ³¹P-magneto-resonance spectroscopic parameters in the frontal lobe, we found phosphocreatine levels and the ratio phosphocreatine/adenosine triphosphate to be increased (12.62±1.98% resp. 0.31±0.06) in 50 neuroleptic-treated schizophrenics, whereas no differences were detected in 10 neuroleptic-free patients (11.66±2.57% resp. 0.29±0.08) compared to 36 controls (11.37±1.45 resp. 0.29±0.04). This result points to a major role of neuroleptics in the metabolism of high-energy phosphates.     

Cerebral lateralization of frontal lobe language processes and lateralization of the posterior visual word processing system

The brain areas involved in visual word processing rapidly become lateralized to the left cerebral hemisphere. It is often assumed this is because, in the vast majority of people, cortical structures underlying language production are lateralized to the left hemisphere. An alternative hypothesis, however, might be that the early stages of visual word processing are lateralized to the left hemisphere because of intrinsic hemispheric differences in processing low-level visual information as required for distinguishing fine-grained visual forms such as letters. If the alternative hypothesis was correct, we would expect posterior occipito-temporal processing stages still to be lateralized to the left hemisphere for participants with right hemisphere dominance for the frontal lobe processes involved in language production. By analyzing event-related potentials of native readers of French with either left hemisphere or right hemisphere dominance for language production (determined using a verb generation task), we were able to show that the posterior occipito-temporal areas involved in visual word processing are lateralized to the same hemisphere as language production. This finding could suggest top-down influences in the development of posterior visual word processing areas.     

Neurophysiological indices of attention to speech in children with specific language impairment.

OBJECTIVE: The aim was to determine whether children with specific language impairment (SLI) differed from children with typical language development (TLD) in their allocation of attention to speech sounds. METHODS: Event-related potentials were recorded to non-target speech sounds in two tasks (passive-watch a video and attend to target tones among speech sounds) in two experiments, one using 50-ms duration vowels and the second using 250-ms vowels. The difference in ERPs across tasks was examined in the latency range of the early negative difference wave (Nd) found in adults. Analyses of the data using selected superior and inferior sites were compared to those using electrical field power (i.e., global field power or GFP). The topography of the ERP at the maximum GFP was also examined. RESULTS: A negative difference, comparable to the adult Nd, was observed in the attend compared to the passive task for both types of analysis, suggesting allocation of attentional resources to processing the speech stimuli in the attend task. Children with TLD also showed greater negativity than those with SLI in the passive task for the long vowels, suggesting that they allocated more attentional resources to processing the speech in this task than the SLI group. This effect was only significant using the GFP analysis and was seen as smaller GFP for the TLD than SLI group. The SLI group also showed significantly later latency than the TLD group in reaching the maximum GFP. In addition, a significantly greater proportion of children with SLI compared to those with typical language showed left-greater-than-right frontocentral amplitude at the latency determined from each child's maximum GFP peak. CONCLUSIONS: Children generally showed greater attention to speech sounds when attention is directed to the auditory modality compared to the visual modality. However, children with TLD, unlike SLI, also appear to devote some attentional resources to speech even in a task in which they are instructed to attend to visual information and ignore the speech. SIGNIFICANCE: These findings suggest that children with SLI have limited attentional resources, that they are poorer at dividing attention, or that they are less automatic in allocating resources to speech compared to children with typically developing language skills.     

Obsessive-compulsive disorder secondary to bilateral frontal damage due to a closed head injury.

OBJECTIVE: To describe a patient who exhibited obsessive-compulsive disorder and frontal lobe dysfunction signs after a closed head trauma. BACKGROUND: Recent evidence indicates that frontal-subcortical circuits are involved in the pathogenesis of primary obsessive-compulsive disorder. There are a number of case reports of secondary obsessive-compulsive disorder after lesions involving certain parts of these circuits. METHOD: Clinical examinations, cognitive and behavioral assessments, and-lesion analysis based on magnetic resonance imaging were conducted. RESULTS: The patient displayed marked obsessive-compulsive behavior along with hyperorality and apathy. Magnetic resonance imaging showed symmetrical frontal-polar abnormal signal intensity. Topographic lesion analysis revealed involvement of Brodmann areas 11, 10, 24, 25, and 32. CONCLUSIONS: The patient presented in this report had both frontal lobe dysfunction signs and obsessive-compulsive disorder secondary to bilateral frontal damage due to a closed head injury. The etiological significance of head injury and frontal lobe involvement in obsessive-compulsive disorder is discussed in the context of the clinical and neuroimaging findings and of previous series of brain injured patients.     

Subdivision of frontal cortex mechanisms for language production in aphasia

Ventrolateral prefrontal cortex (VLPFC) has long been linked to language production, but the precise mechanisms are still being elucidated. Using neuropsychological case studies, we explored possible sub-specialization within this region for different linguistic and executive functions. Frontal patients with different lesion profiles completed two sequencing tasks, which were hypothesized to engage partially overlapping components. The multi-word priming task tested the sequencing of co-activated representations and the overriding of primed word orders. The sequence reproduction task tested the sequencing of co-activated representations, but did not employ a priming manipulation. We compared patients' performance on the two tasks to that of healthy, age-matched controls. Results are partially consistent with an anterior–posterior gradient of cognitive control within lateral prefrontal cortex (Koechlin & Summerfield, 2007). However, we also found a stimulus-specific pattern, which suggests that sub-specialization might be contingent on type of representation as well as type of control signal. Isolating such components functionally and anatomically might lead to a better understanding of language production deficits in aphasia.     

Italian neuropsychological instruments to assess memory,attention and frontal functions for developmental age

Abstract In this study, a series of tests exploring long-term verbal memory (the Short Story Test), attention (a modified version of Attentional Matrices and the Trail Making Test) and frontal functions (a modified version of the Frontal Assessment Battery) have been standardised on an Italian population of 283 children aged 5–14. Raw scores for each test have been adjusted for a series of variables (child's age, years of parents' education, handedness, gender) and transformed in equivalent scores enabling direct comparison across measures. This study was promoted by LICE (the Italian League Against Epilepsy) in order to provide Italian instruments standardised on the developmental age population and to study some of the most frequently impaired cognitive functions in epilepsy.     

Preserved leftward movement in left unilateral spatial neglect due to frontal lesions.

Three patients with left unilateral spatial neglect after predominantly frontal lobe lesions were asked to extend a horizontal line leftwards to double its original length. In this line extension task, they readily executed movements in or towards the contralesional left space. They performed the task in the left and right hemispaces as well as in the midline. The mean extension lengths did not differ significantly among these three spatial conditions. These results suggest that directional hypokinesia takes little part in left unilateral spatial neglect due to frontal lobe lesions. It is considered that the patients could execute leftward movements as the task oriented their attention sufficiently to the left. Two of the three patients, like reported cases with frontal neglect, showed a typical exploratory deficit for the left space in the line cancellation test. Such a deficit found in the traditional tasks, however, does not mean the presence of directional hypokinesia. All three patients showed visual extinction on double simultaneous stimulation. An attentional mechanism seems to play a predominant part in unilateral spatial neglect due to frontal lesions.     

Magnetic sources of the M50 response are localized to frontal cortex.

OBJECTIVE: To determine the source localization(s) of the midlatency auditory magnetic response M50, the equivalent of the P50 potential, a sleep state-dependent waveform known to habituate to repetitive stimulation. METHODS: We used a paired stimulus paradigm at interstimulus intervals of 250, 500 and 1000 ms, and magnetoencephalographic (MEG) recordings were subjected to computational methods for current density reconstruction, blind source separation, time-frequency analysis, and data visualization to characterize evoked dynamics. RESULTS: Each subject showed localization of a source for primary auditory evoked responses in the region of the auditory cortex, usually at a 20-30 ms latency. However, responses at 40-70 ms latency that also decreased following the second stimulus of a pair were not localizable to the auditory cortex, rather showing multiple sources usually including the frontal lobes. CONCLUSIONS: The M50 response, which shows habituation to repetitive stimulation, was not localized to the auditory cortex, but showed multiple sources including frontal lobes. SIGNIFICANCE: These MEG results suggest that sources for the M50 response may represent non-auditory, perhaps arousal-related, diffuse projections to the cortex.     

Disruption of attention to novel events after frontal lobe injury in humans

OBJECTIVE: To investigate whether frontal lobe damage in humans disrupts the natural tendency to preferentially attend to novel visual events in the environment. METHODS: Nine patients with chronic infarctions in the dorsolateral prefrontal cortex (DLPFC) and 23 matched normal controls participated in a study in which subjects viewed repetitive background stimuli, infrequent target stimuli, and novel visual stimuli (for example, fragmented or "impossible" objects). Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at the different kinds of stimuli, and the target detection accuracy and speed served as dependent variables. RESULTS: Overall, normal controls spent significantly more time than frontal lobe patients looking at novel stimuli. Analysis of responses across blocks showed that initially frontal lobe patients behaved like normal controls by directing more attention to novel than background stimuli. However, they quickly began to distribute their viewing time evenly between novel and background stimuli, a pattern that was strikingly different from normal controls. By contrast, there were no differences between frontal lobe patients and normal controls for viewing duration devoted to background and target stimuli, target detection accuracy, or reaction time to targets. Frontal lobe patients did not differ from normal controls in terms of age, education, estimated IQ, or mood, but were more apathetic as measured by self report and informants' judgments. Attenuated responses to novel stimuli significantly correlated with degree of apathy. CONCLUSIONS: This study demonstrates that DLPFC injury selectively impairs the natural tendency to seek stimulation from novel and unusual stimuli. These data provide the first quantitative behavioural demonstration that the human frontal lobes play a critical part in directing and sustaining attention to novel events. The impairment of novelty seeking behaviour may contribute to the characteristic apathy found in patients with frontal lobe injury.     

Mild visual acuity disturbances are associated with performance on tests of complex visual attention in MS.

Because MS patients frequently report visual acuity disturbances, neuropsychologists often screen patients for severe visual acuity disturbances and tailor test batteries that minimize the need for intact vision. Less is known about how mild visual acuity disturbances may influence neuropsychological test performance. This study examined the extent to which mild visual acuity disturbances influence performance on visually-based tests of complex attention. Relapsing-remitting and secondary progressive MS patients who reported adequate vision were recruited for this study. A battery was administered that included the oral version of the Symbol Digit Modalities Test (SDMT), the Visual Elevator (VE) subtest from the Test of Everyday Attention, and a reduced near vision eye chart. Results suggested that, in addition to measuring higher order cognitive processes, visual tests of attention are sensitive to mild primary visual disturbances in MS.     

Impairments of emotion and real-world complex behavior following childhood- or adult-onset damage to ventromedial prefrontal cortex.

The behavioral syndrome resulting from damage to the ventromedial prefrontal (VM) region presents major challenges for clinical assessment and management, stemming from the absence of reliable neurologic or psychometric markers, coupled with often debilitating impairments of decision-making and behavior regulation. Damage to this region disrupts neural circuitry critical for emotion, which in turn may contribute to impairments in real-world competencies. Here we present findings from patients with focal lesions in the VM region acquired either in childhood or adulthood, and show that there is a relationship between emotional dysfunction and impairments in real-world behavioral competencies. Emotion was rated by participants' relatives on dimensions including frustration tolerance, lability, anxiety, and blunted affect. Real-world competencies were rated by the relatives on dimensions including judgment, planning, and initiation, and were evaluated by clinician ratings in areas including social, financial, and occupational function. VM damage resulted in severe disruption of emotion, and this emotional dysfunction accounted for a significant portion of impaired real-world competencies. The long-term impairments associated with childhood-onset lesions were at least as severe as those resulting from adult-onset damage. Greater focus on the contribution of emotional dysfunction to the real-world competencies of patients with damage in the VM region may sharpen their neuropsychological assessment and facilitate rehabilitation efforts.