Lateral Frontal Activity Research Articles

Dynamic variation in pleasure in children predicts nonlinear change in lateral frontal brain electrical activity.

Individual variation in the experience and expression of pleasure may relate to differential patterns of lateral frontal activity. Brain electrical measures have been used to study the asymmetric involvement of lateral frontal cortex in positive emotion, but the excellent time resolution of these measures has not been used to capture second-by-second changes in ongoing emotion until now. The relationship between pleasure and second-by-second lateral frontal activity was examined with the use of hierarchical linear modeling in a sample of 128 children ages 6-10 years. Electroencephalographic activity was recorded during "pop-out toy," a standardized task that elicits pleasure. The task consisted of 3 epochs: an anticipation period sandwiched between 2 play periods. The amount of pleasure expressed during the task predicted the pattern of nonlinear change in lateral frontal activity. Children who expressed increasing amounts of pleasure during the task exhibited increasing left lateral frontal activity during the task, whereas children who expressed contentment exhibited increasing right/decreasing left activity. These findings indicate that task-dependent changes in pleasure relate to dynamic, nonlinear changes in lateral frontal activity as the task unfolds.

Differentiating early and late‐onset depression with multichannel near‐infrared spectroscopy

AbstractBackground: Individuals with late‐life depression can be divided into two categories, those with early and late‐onset depression (EOD and LOD, respectively). It has been reported that LOD has more accentuated subcortical vascular lesions and frontal lobe dysfunction (hypofrontality). The aim of the present study was to examine whether LOD exhibits more prominent hypofrontality than EOD during performance of the word fluency task (WFT) under multichannel near‐infrared spectroscopy (NIRS), a newly developed non‐invasive functional neuroimaging technique.Methods: Eleven patients with EOD, 12 patients with LOD, and 13 healthy controls participated in the study. Clinical symptoms of depression were equivalent in the EOD and LOD groups. Brain magnetic resonance imaging demonstrated more robust subcortical vascular changes in LOD than EOD. The NIRS images were obtained using an ETG‐4000, 52‐channel NIRS system (Hitachi Medical, Tokyo, Japan). Mean changes in oxy‐hemoglobin (oxy‐Hb) were evaluated while the participants performed the phonemic WFT.Results: Healthy controls exhibited clear increases in oxy‐Hb bilaterally throughout the medial to the lateral frontal cortices and the superior temporal areas during the WFT. In contrast, increases in oxy‐Hb were mildly attenuated in EOD and severely attenuated in LOD in most channels. Subsequent analyses revealed that increases in oxy‐Hb in LOD during the WFT was significantly poorer than in EOD in the left lateral portion of the cortex, including the dorsolateral prefrontal and the superior temporal areas. In addition, significant negative correlations were obtained between the age of onset and oxy‐Hb, as well as between subcortical vascular changes and oxy‐Hb in the lateral channels. These findings suggest that the higher the age of onset of depression, and the more prominent the vascular lesions, the greater the attenuation in lateral frontal and temporal activation, as indicated by NIRS.Conclusions: Multichannel NIRS is useful for demonstrating attenuated functional activation in the left lateral prefrontal and temporal areas in LOD and, thus, for differentiating between LOD and EOD. The NIRS findings observed may have useful clinical implications for treatment‐resistant LOD.

Anterior asymmetry, defensiveness, and perceptions of parental caring

Perceived parental caring and relative left frontal activation (LFA) of the electroencephalogram (EEG) have been associated with salutary mental and physical health benefits. Defensiveness on the other hand, is associated with decreased self-reported and other-reported psychopathology, and physical health liabilities. Though previous work has delineated relations among some of these factors (e.g. LFA and defensiveness, LFA and immune function, parental caring and defensiveness), the interrelationship of defensiveness, LFA, and parental caring is unknown. The present study examined relationships among defensiveness, perceived parental caring, and resting anterior asymmetry of the electroencephalogram. Defensiveness and perceived maternal caring contributed significant unique variance to the prediction of relative left lateral frontal activation. Paternal caring did not correlate with left frontal activation. The results are discussed as they relate to the relevance of these factors for physical and mental health.

Abnormal response inhibition in criminal psychopaths: Evidence from event-related fMRI

Introduction Psychopathy is a personality disorder characterised by disturbance in affective, interpersonal, and behavioural domains. Typically, it is the behavioural disturbances, including impulsivity, poor behavioural controls, and persistent contravention of societal norms, that brings the psychopath to the attention of society. The psychopaths’ behavioural disturbance has been conceptualized as arising from impaired response inhibition. Event-related potential research (Kiehl et al., 2000, Biological Psychiatry, 48) suggests that psychopathy is associated with abnormal neural activity during suppression of inappropriate responses. We used event-related fMRI to elucidate the neurobiological correlates of response inhibition during performance of a Go/NoGo task. Using this task in healthy controls Liddle et al. (2001, Human Brain Mapping, 12) demonstrated the importance of lateral frontal cortex in response inhibition. We hypothesised that psychopaths would show less activation in lateral frontal cortex during processing of NoGo stimuli than would healthy controls. Methods Fourteen psychopaths were recruited from a maximum-security prison and compared with fourteen healthy control participants selected from the general population. Psychopathy was assessed using the Hare Psychopathy Checklist-Revised (PCL-R) (Hare, 1991). Groups were matched for age, parental socioeconomic status, and IQ. All participants were right-handed, native English speakers, without history of head injury or psychotic illness. Task procedures are as described in Liddle et al. (2001). The visual stimuli for the Go and NoGo trials were the letters ‘X’ and ‘A’ respectively, presented for a period of 250 msecs each. Each trial commenced with a descending count of asterisks in order to increase motor response preparation. Twenty-four Go and 24 NoGo trials were randomly presented in a single scanning session. Imaging was performed using a General Electric 1.5 T whole body system fitted with a Horizon echo-speed upgrade. Functional image volumes were collected with a gradient-echo sequence (TR/IE 2500/50 ms, flip angle 90”, FOV 24x24 cm, 64x64 matrix, 62.5 kHz bandwidth, 3.75x3.75 mm in plane resolution, 4 mm slice thickness, 29 slices). Functional images were realigned, normalised, and smoothed using Statistical Parametric Mapping (SPM99). Event-related responses to the Go and NoGo stimuli were modeled with a synthetic haemodynamic response function composed of two gamma functions and their temporal derivatives. To test the hypothesis of reduced activation in lateral frontal cortex in psychopaths, we tested for significant group differences in activation during NoGo trials within I0mm diameter spherical regions centred on the loci of activation in lateral frontal cortex reported by Liddle et al. (2001). Results No significant differences between groups in accuracy of performance were observed. In accordance with the hypothesis, psychopaths exhibited significantly less activation in lateral frontal cortex, bilaterally, than healthy controls during NoGo trials: xyz = -48 -4 52, Z=3.78; xyz = 36 0 36, Z=3.66. Discussion We have demonstrated that inhibiting a behavioural response is associated with less lateral frontal activation in psychopaths compared to healthy control subjects. This is consistent with previous electrophysiological findings. Kiehl et al. (2000) reported that psychopaths exhibited a reduced amplitude of the frontal negative potential (N275) during NoGo trials. Taken together, these findings indicate that the cerebral mechanism for response inhibition is impaired in psychopathy.

Neural Response during Preference and Memory Judgments for Subliminally Presented Stimuli: A Functional Neuroimaging Study

Preexposing subjects to visual stimuli is sufficient to establish a subsequent preference, even when previous exposure is subliminal, such that explicit recognition is at chance. This influence of previous exposure on preference judgments, known as the "mere exposure effect," is a form of unconscious memory. The present functional neuroimaging study examines the mechanism of this effect. Nine volunteer subjects were studied using functional imaging while making forced choice judgments about abstract stimuli on the basis of either preference or memory. Each judgment type was made under two conditions: under one condition one or the other stimulus had previously been presented subliminally, whereas under the second condition both stimuli were novel. Memory judgments were associated with activation of left frontopolar cortex and parietal areas, whereas preference judgments were associated with activation of medial prefrontal cortex and regions of occipital cortex. The modulation of preference by objective familiarity (implicit memory) was associated with right lateral frontal activation. Significant activation of hippocampal gyrus was seen in response to objective stimulus novelty, regardless of judgment type required. Our data thus demonstrate activations of a memory system independent of recollective experience. Dissociable activations within this system implicate a frontopolar involvement in explicit retrieval attempt and right lateral prefrontal cortex involvement in implicit memory expressed in preference judgments. Furthermore, the results suggest that hippocampal response to stimulus novelty can be independent of conscious reportability of familiarity.

Attention to One or Two Features in Left or Right Visual Field: A Positron Emission Tomography Study

In human vision, two features of the same object can be identified concurrently without loss of accuracy. Performance declines, however, when the features belong to different objects in opposite visual fields. We hypothesized that different positron emission tomography activation patterns would reflect these behavioral results. We first delineated an attention network for single discriminations in left or right visual field and then compared this with the activation pattern when subjects divided attention over two features of a single object or over two objects in opposite hemifields. When subjects attended to a single feature, parietal, premotor, and anterior cingulate cortex were activated. These effects were strongest in the right hemisphere and were, remarkably, unaffected by the direction of attention. In contrast, direction of attention affected occipital and frontal activity: right occipital and left lateral frontal activity were higher with attention to the left, whereas right lateral frontal activity was higher with attention to the right. When subjects identified two features of the same object, parietal, premotor, and anterior cingulate activity was enhanced further, predominantly this time in the left hemisphere. Again, there was no direction sensitivity. Direction-sensitive activation of lateral frontal cortex also was increased. Finally, when subjects divided their attention over opposite hemifields, activity in the direction-sensitive occipital and frontal regions fell to a level midway between those seen during exclusively leftward or rightward attention. Thus, the behavioral efficiency with which we attend to multiple features of a single peripheral object is paralleled by enhanced activity in structures generally active during peripheral selective attention as well as in structures that depend on the specific direction of attention, most notably lateral frontal cortex. In addition, in the direction-sensitive regions, dividing attention over hemifields causes a compromise pattern between the extreme levels obtained during unilateral attention.

Cortical-striatal-thalamic circuits and brain glucose metabolic activity in 70 unmedicated male schizophrenic patients

The cortical-striatal-thalamic circuit modulates cognitive processing and thus may be involved in the cognitive dysfunction in schizophrenia. The imaging of metabolic rate in the structures making up this circuit could reveal the correlates of schizophrenia and its main symptoms. Seventy male schizophrenic patients underwent [18F]-fluorodeoxyglucose positron emission tomography after a period of at least 4 weeks during which they had not received neuroleptic medication and were compared to 30 age-matched male normal comparison subjects. Analyses revealed decreased metabolism in medial frontal cortex, cingulate gyrus, medial temporal lobe, corpus callosum, and ventral caudate and increased metabolism in the left lateral temporal and occipital cortices in the schizophrenic cohort. Consistent with previous studies, the schizophrenic group had lower hypofrontality scores (ratios of lateral frontal to occipital metabolism) than did comparison subjects. The lateral frontal cortical metabolism of schizophrenic patients did not differ from that of comparison subjects, while occipital cortical metabolism was high, suggesting that lateral hypofrontality is due to abnormalities in occipital rather than lateral frontal activity. Hypofrontality was more prominent in medial than lateral frontal cortex. Brief Psychiatric Rating Scale (BPRS) scores, obtained for each schizophrenic patient on the scan day, were correlated with regional brain glucose metabolic rate. Medial frontal cortical and thalamic activity correlated negatively with total BPRS score and with positive and negative symptom scores. Lateral frontal cortical metabolism and hypofrontality scores did not significantly correlate with negative symptoms. Analyses of variance demonstrated a reduced right greater than left asymmetry in the schizophrenic patients for the lateral cortex as a whole, with simple interactions showing this effect specifically in temporal and frontal cortical regions. Low metabolic rates were confirmed in medial frontal cortical regions as well as in the basal ganglia, consistent with the importance of the cortical-striatal-thalamic pathways in schizophrenia. Loss of normal lateralization patterns was also observed on an exploratory basis. Correlations with negative symptoms and group differences were more prominent in medial than lateral frontal cortex, suggesting that medial regions may be more important in schizophrenic pathology.