PET study of brain maintenance of verbal creative activity.

This paper deals with the investigation of the brain organization of verbal creativity. Psychological tasks were designed in accordance with two main strategies used by volunteers in solving creative tasks. Regional cerebral blood flow (rCBF) was measured with positron emission tomography (PET) when performing two types of creative tasks in two groups of subjects, each type of the task organizing the creativity process in its own way. Valuable brain correlates of creativity were revealed in the left parieto-temporal regions (Brodmann areas 39 and 40).     

Functional mapping of human brain in olfactory processing: a PET study

This study describes the functional anatomy of olfactory and visual naming and matching in humans, using positron emission tomography (PET). One baseline control task without olfactory or visual stimulation, one control task with simple olfactory and visual stimulation without cognition, one set of olfactory and visual naming tasks, and one set of olfactory and visual matching tasks were administered to eight normal volunteers. In the olfactory naming task (ON), odors from familiar items, associated with some verbal label, were to be named. Hence, it required long-term olfactory memory retrieval for stimulus recognition. The olfactory matching task (OM) involved differentiating a recently encoded unfamiliar odor from a sequentially presented group of unfamiliar odors. This required short-term olfactory memory retrieval for stimulus differentiation. The simple olfactory and visual stimulation resulted in activation of the left orbitofrontal region, the right piriform cortex, and the bilateral occipital cortex. During olfactory naming, activation was detected in the left cuneus, the right anterior cingulate gyrus, the left insula, and the cerebellum bilaterally. It appears that the effort to identify the origin of an odor involved semantic analysis and some degree of mental imagery. During olfactory matching, activation was observed in the left cuneus and the cerebellum bilaterally. This identified the brain areas activated during differentiation of one unlabeled odor from the others. In cross-task analysis, the region found to be specific for olfactory naming was the left cuneus. Our results show definite recruitment of the visual cortex in ON and OM tasks, most likely related to imagery component of these tasks. The cerebellar role in cognitive tasks has been recognized, but this is the first PET study that suggests that the human cerebellum may have a role in cognitive olfactory processing as well.     

The functions of processing on states of awareness in the Remember/Know paradigm: a study of using verbal materials

The nature of recollective experience was investigated in two recognition memory tasks. Subjects gave "Remember" judgments to recognized items that were accompanied by conscious recollection and "Know" judgments to recognized items that were familiarity of events without recollection on recognition. High-familiarity words that are based on conceptual and semantic information enhanced "Remember" judgments. In contrast, compared with high-familiarity words low-familiarity words that are caused perceptual fluency enhanced "Know" judgments (Experiment 1). In Experiment 2, spacing effect, an advantage in memory for information repeated at separate points of time over information repeated in massed fashion was found for "Remember" judgments. However, spacing effect disappeared for "Remember" judgments when memory load was high at study. These findings are interpreted as providing further support for the idea that recognition memory entails two distinct components, one based on elaborative information, the other based on perceptual fluency.     

Sex differences in prefrontal cortical brain activity during fMRI of auditory verbal working memory

Functional imaging studies of sex effects in working memory (WMEM) are few, despite significant normal sex differences in brain regions implicated in WMEM. This functional MRI (fMRI) study tested for sex effects in an auditory verbal WMEM task in prefrontal, parietal, cingulate, and insula regions. Fourteen healthy, right-handed community subjects were comparable between the sexes, including on WMEM performance. Per statistical parametric mapping, women exhibited greater signal intensity changes in middle, inferior, and orbital prefrontal cortices than men (corrected for multiple comparisons). A test of mixed-sex groups, comparable on performance, showed no significant differences in the hypothesized regions, providing evidence for discriminant validity for significant sex differences. The findings suggest that combining men and women in fMRI studies of cognition may obscure or bias results.     

Using magnetoencephalography to investigate brain activity during high frequency deep brain stimulation in a cluster headache patient

Purpose:

Treatment-resistant cluster headache can be successfully alleviated with deep brain stimulation (DBS) of the posterior hypothalamus [1]. Magnetoencephalography (MEG) is a non-invasive functional imaging technique with both high temporal and high spatial resolution. However, it is not known whether the inherent electromagnetic (EM) noise produced by high frequency DBS is compatible with MEG.

Materials and methods:

We used MEG to record brain activity in an asymptomatic cluster headache patient with a DBS implanted in the right posterior hypothalamus while he made small movements during periods of no stimulation, 7 Hz stimulation and 180 Hz stimulation.

Results:

We were able to measure brain activity successfully both during low and high frequency stimulation. Analysis of the MEG recordings showed similar activation in motor areas in during the patient’s movements as expected. We also observed similar activations in cortical and subcortical areas that have previously been reported to be associated with pain when the patient’s stimulator was turned on or off [2,3].

Conclusion:

These results show that MEG can be used to measure brain activity regardless of the presence of high frequency deep brain stimulation.     

Specificity of regional brain activity in anxiety types during emotion processing

The present study tested the hypothesis that anxious apprehension involves more left- than right-hemisphere activity and that anxious arousal is associated with the opposite pattern. Behavioral and fMRI responses to threat stimuli in an emotional Stroop task were examined in nonpatient groups reporting anxious apprehension, anxious arousal, or neither. Reaction times were longer for negative than for neutral words. As predicted, brain activation distinguished anxious groups in a left inferior frontal region associated with speech production and in a right-hemisphere inferior temporal area. Addressing a second hypothesis about left-frontal involvement in emotion, distinct left frontal regions were associated with anxious apprehension versus processing of positive information. Results support the proposed distinction between the two types of anxiety and resolve an inconsistency about the role of left-frontal activation in emotion and psychopathology.     

Influence of muscle activity on brain oxygenation during verbal fluency assessed with functional near-infrared spectroscopy

A large part of the literature of functional near-infrared spectroscopy (fNIRS) deals with overt verbal fluency. It has been claimed that fNIRS has a low susceptibility to movement related artefacts as, for example, associated with overt speech. However, so far, no study has investigated this assumption in an experimental design. Therefore, we examined a group of 16 healthy subjects during performance of two verbal fluency tasks (experiment 1: phonological fluency; experiment 2: semantical fluency, paced answers, pronouncing vs. writing). We measured changes of oxygenated (O₂Hb) and deoxygenated haemoglobin (HHb) over fronto-temporal (brain) areas via fNIRS, while temporalis muscle activity was simultaneously assessed by means of electromyography (EMG). Statistical analyses indicated comparable word production, higher increases of O₂Hb and higher decreases of HHb over fronto-temporal areas during word fluency in contrast to the control task weekday reciting. This fNIRS pattern indicates fluency related activation and was found for pronouncing and for writing in both experiments. Regarding the EMG data, fluency related activity was only found for pronouncing, not for writing. Thus, muscle activity cannot account for fluency related fNIRS activity during writing. Additionally, correlation analyses showed no systematic associations of fNIRS and EMG signals. In conclusion, we found arguments that fNIRS actually allows for the measurement of brain activity over fronto-temporal areas during verbal fluency. Nonetheless, further studies should evaluate more direct associations between fNIRS and EMG signals by specific experimental manipulations and data analysing approaches that allow dealing fNIRS and EMG raw data simultaneously.     

Neural correlates of age-related verbal episodic memory decline: a PET study with combined subtraction/correlation analysis

Using PET, we have determined the neural substrates of age-related verbal episodic memory decline. Twelve young and twelve older healthy volunteers (mean age; 22 and 59 years, respectively) were scanned while performing encoding and retrieval tasks. Retrieval performance was lower in old than in young subjects. The PET data were analyzed using a combined subtraction/correlation approach. Classic subtraction disclosed prefrontal rCBF increases common to both groups, distributed bilaterally during encoding and exclusively right-sided during retrieval, without between-group differences. The correlation analysis between PET activity during encoding and subsequent retrieval performance revealed significant correlations for the left hippocampal region in both groups, but for the right inferior frontal gyrus in the older subjects only. Thus, lower performance in older subjects during an episodic retrieval task may reflect a combination of (i) subtle encoding dysfunction, evidenced by more widespread activity-performance correlations and (ii) less efficient retrieval, as evidenced by unaltered activation pattern (as revealed by the classic subtraction method) despite reduced performance. These exploratory findings suggest the aged brain may be unable to compensate for reduced efficiency of right prefrontal cortex by additional left frontal activation.     

Comparison of brain activity during different types of proprioceptive inputs: a positron emission tomography study

It has been shown that the primary and secondary somatosensory cortex, as well as the supplementary motor area (SMA), are involved in central processing of proprioceptive signals during passive and active arm movements. However, it is not clear whether different cortical areas are involved in processing of different proprioceptive inputs (skin, joint, muscle receptors), what their relative contributions might be, where kinesthetic sensations are formed within the CNS, and how they interact when the full peripheral proprioceptive machinery acts. In this study we investigated the representation of the brain structures involved in the perception of passive limb movement and illusory movement generated by muscle tendon vibration. Changes in cortical activity as indicated by changes in regional cerebral blood flow (rCBF) were measured using positron emission tomography (PET). Twelve subjects were studied under four conditions: (1) passive flexion-extension movement (PM) of the left forearm; (2) induced illusions of movements (VI) similar to the real PM, induced by alternating vibration of biceps and triceps tendons (70-80 Hz) at the elbow; (3) alternating vibration of biceps and triceps tendons (with 20-50 Hz) without induced kinesthetic illusions (VN); and (4) rest condition (RE). The results show different patterns of cortex activation. In general, the activation during passive movement was higher in comparison with both kinds of vibration, and activation during vibrations with induced illusions of movement was more prominent than during vibrations without induced illusions. When the PM condition was contrasted with the other conditions we found the following areas of activation -- the primary motor (MI) and somatosensory area (SI), the SMA and the supplementary somatosensory area (SSA). In conditions where passive movements and illusory movements were contrasted with rest, some temporal areas, namely primary and associative auditory cortex, were activated, as well as secondary somatosensory cortex (SII). Our data show that different proprioceptive inputs, which induce sensation of movement, are associated with differently located activation patterns in the SI/MI and SMA areas of the cortex. In general, the comparison of activation intensities under different functional conditions indicates the involvement of SII in stimulus perception generation and of the SI/MI and SMA areas in the processing of proprioceptive input. Activation of the primary and secondary auditory cortex might reflect the interaction between somatosensory and auditory systems in movement sense generation. SSA might also be involved in movement sense generation and/or maintenance.     

Spatio-temporal analysis of electric brain activity during semantic and phonological word processing.

There is an ongoing debate in cognitive neuroscience about the time course and the functional independence of the different processes involved in encoding written language material. New data indicate very fast and highly parallel language analysis networks in the brain. Here we demonstrate a methodological approach to study the temporal dynamics of this network by searching for time periods where different task demands emphasize different aspects of the network. Multi-channel event related potentials (ERPs) were recorded during a semantic and a phonological reading task from 14 healthy subjects. Signals were analyzed exclusively on the basis of the spatial configuration of the electric potential distributions (ERP maps), since differences in these spatial patterns directly reflect changes in the configuration of the active sources in the brain. This analysis did not reveal any differences of the evoked brain electric fields between the two tasks up to 280 ms post-stimulus. The ERP maps then differed for a brief period between 280 and 380 ms, before they were similar again. The analysis of the maps using a global linear localization procedure revealed a network of areas, active in both tasks, that mainly involved the left postero-temporal and left antero-temporal regions. The left posterior activation was found already around 100 ms post-stimulus, indicating that language-specific functions appear early in time. We therefore conclude that phonological and semantic processing are essentially performed in both tasks and that only late decision-related processes influence the relative strength of activity of the different modules in the complex language network.     

Transdiagnostic trauma severity in anxiety and mood disorders: Functional brain activity during emotional scene processing

Exposure to traumatic events is not unique to post-traumatic stress disorder (PTSD) and is a significant factor in the development of physical and mental disease across the diagnostic spectrum. Using fMRI, this study assesses functional activation in the amygdala and visual cortex during emotional scene processing in a sample of anxiety and mood disorder patients (N = 162). Replicating previous studies with healthy young participants, a strong covariation was found between functional activity in the amygdala and ventral visual cortex, with blood-oxygen-level dependent (BOLD) activity overall significantly enhanced in both regions when viewing emotionally arousing, compared to neutral, scenes. BOLD changes during emotional processing predicted questionnaire reports of experienced trauma and PTSD-like symptoms (e.g., intrusive thoughts, bad dreams, re-experiencing) and associated functional impairment. Patients showing the smallest BOLD changes when viewing emotional (compared to neutral) scenes in the amygdala and ventral visual cortex reported the highest trauma scores, whereas those patients with the largest amygdala emotional reactivity differences reported the lowest trauma scores. Experiencing a life-threatening event (to self or other) that prompts high fear, distress, and functional impairment was associated with reduced functional limbic-visual activity, independent of a PTSD diagnosis. The findings suggest that experienced trauma may be a transdiagnostic vulnerability factor contributing significantly to psychopathology in many patients with anxiety and mood disorders.     

Neural substrates associated with evaluative processing during co-activation of positivity and negativity: a PET investigation

Affective symmetries, such as the positivity offset and negativity bias, have been postulated to be attributable to distinct activation functions of the positive and negative affect systems. We investigated the neural substrates that are engaged when the positive and negative affect systems undergo parallel and integrative processing. Eleven subjects were scanned using H(2)(15)O PET during choosing the subjective feeling produced by a stimulation pair of pictures or words. Four different conditions were designed for contrast: pure positivity, pure negativity, positivity offset, and negativity bias. The dorsolateral prefrontal activation was associated with positivity offset and negativity bias condition, whereas the ventromedial prefrontal activation, together with limbic and subcortical activations, was associated with pure positivity and pure negativity condition. The results indicated that positivity offset and negativity bias are not merely due to asymmetric activations of the positive and negative systems, but integrative processing of higher neocortical levels is involved.     

咨询师的言语活动水平与会谈深度的过程-效果研究

目的:检验咨询师的言语活动水平与咨询会谈深度的关系.方法:在一所大学的咨询中心选取28个咨询会谈进行录像,咨询师和来访者在会谈结束时分别填写会谈评估问卷(SEQ),测量双方对会谈深度的评价.根据会谈深度三维模型(包括情感、个人化、时间3个维度)对录像资料进行评定,同时计算咨询师的言语活动所占会谈时间的比例,用以衡量咨询师的言语活动水平.结果:咨询师言语活动占整个会谈的时间比例为(41±15)％.咨询师的言语活动水平与会谈深度三维模型中的情感、时间维度负相关(r=-0.65、-0.44,均P＜0.05),与个人化维度无相关(r=-0.27,P＞0.05).咨询师的言语活动水平与当事人对会谈深度的评价正相关(r =0.59,P＜0.01),但与咨询师对会谈深度的评价无相关(r=-0.09,P ＞0.05).结论:咨询师的言语活动水平越高,当事人对咨询会谈的评价越积极,咨询师对咨询会谈则有不同的评价.     

Computer phantom study of brain PET glucose metabolism imaging using a rotating SPECT/PET camera

Positron emission tomography (PET) with [18F] fluoro-deoxy-glucose (FDG) provides information about glucose metabolism and is used to measure tissue glucose kinetics in the brain. The recent interest in hybrid SPECT/PET systems emerged as a practical approach to reduce the high cost of purchasing a dedicated ring-detector PET system. We have implemented interpolation methods for processing the projection data that could potentially reduce artifacts when reconstructing a dynamic imaging sequence in a PET study from a dual-head rotating SPECT/PET system. The computer simulations predict that parameter estimates from the dedicated PET system will be superior to results using the rotating camera system. However, the rotating camera system using projection interpolation may approach the accuracy of the dedicated PET system if the data noise is below 20%.     

Anatomy of verbal memory: a functional MRI study

The recent advent of new functional neuroimaging techniques such as functional magnetic resonance imaging (fMRI) makes it possible to examine cerebral activations in healthy individuals. In the present study, we attempted to examine the anatomical distribution of neocortical and mediotemporal activations in control subjects during episodic memory tasks over 24 h. BOLD (blood oxygenation-level-dependent) fMRI data were collected from 10 control subjects. Twenty-two contiguous images covering the whole brain were acquired using an EPI echoplanar sequence. Subjects were instructed to learn a list of 17 words, and to recall it immediately and after a 24-h interval. Individual and group analyses were performed using SPM96. The results demonstrated that a similar left occipito-temporofrontal network was activated during both immediate and 24-h-delayed retrieval conditions. In addition, the 24-h-delayed retrieval also activated a larger parietal region and the right hippocampus. These findings suggest that fMRI is a reliable method with which to perform anatomical studies.     

Information processing during physical exercise: a chronometric and electromyographic study

We compared quantitatively the psychometric capacity of human subjects to detect path-guided apparent motion (PAM) and the accuracy of cell ensembles in area 7a to code the same type of stimuli. Nine human subjects performed a detection task of PAM. They were instructed to indicate with a key-press whether they perceived a circularly moving object when five stimuli were flashed successively at the vertices of a regular pentagon. The stimuli were presented along a low contrast circular path with one of 33 speeds (150–600°/s). The average psychometric curve revealed that the threshold for PAM detection was 314°/s. The minimum and maximum thresholds for individual subjects were 277° and 378°/s, respectively. In addition, the activity of cells in area 7a that were modulated by the stimulus position in real or apparent motion was used in a multivariate linear regression analysis to recover the stimulus position over time. Real stimulus motion was decoded successfully from neural ensemble activity at all speeds. In contrast, the decoding of PAM was poor at low stimulus speeds but improved markedly above 300°/s: in fact, this was very close to the threshold above for human subjects to perceive continuous stimulus motion in this condition. These results suggest that the posterior parietal cortex is part of a high-level system that is directly involved in the dynamic representation of complex motion     

Placebo analgesia: a PET study

Placebo analgesia involves complex mechanisms and sometimes has a marked effect on patients in pain. In this study we examined changes in regional cerebral blood flow (rCBF) under three different conditions (resting, hot, painful) before and after placebo administration using H₂¹⁵O and positron emission tomography in ten healthy subjects. In five subjects, placebo administration significantly decreased pain-intensity score (placebo responders), and rCBF in the medial prefrontal cortex (MPFC), posterior parietal cortex (PPC), and inferior parietal lobe (IPL) increased after placebo administration compared with before placebo administration under the painful condition. Furthermore, in the placebo responders, rCBF in the MPFC, PPC and IPL also increased under the resting condition (without sensory stimulation) after placebo administration compared with before placebo administration. However, there was no rCBF change under the rest condition in the placebo nonresponders after placebo administration. These results suggest that placebo analgesia has its effect under the resting condition and MPFC, IPL and PPC may have an important role in placebo analgesia.     

Spontaneous and evoked activity of neurons in deep structures of the brain during their anodal polarization

The influence of anodal polarization on the spontaneous activity of neurons in the caudate nucleus, medial geniculate body, and the median center of the thalamus and on the evoked impulse activity of neurons in the medial geniculate body was investigated during auditory stimulation. The impulse activity was recorded extracellularly with glass and metallic microelectrodes. Nichrome polarizing electrodes of 0.2 mm diameter with an uninsulated tip of 0.3 mm were inserted into the foregoing structures in a packet. Current parameters evoking the reversible suppression of spontaneous and evoked neuronal activity were determined: 300–500 A during exposure for 1–3 min at a distance of up to 3 mm from the polarizing electrode. After the cessation of polarization, a prolonged aftereffect was observed: The inhibition of evoked discharges lasted 4–10 min, and the evoked impulse responses disappeared for 5–20 min.Translated from Fiziologicheskii Zhurnal SSSR imeni I. M. Sechenova, Vol. 71, No. 6, pp. 681–687, June, 1985.     

Correlation of within-individual fluctuation of depressed mood with prefrontal cortex activity during verbal working memory task: optical topography study

Previous studies showed that interindividual variations in mood state are associated with prefrontal cortex (PFC) activity. In this study, we focused on the depressed-mood state under natural circumstances and examined the relationship between within-individual changes over time in this mood state and PFC activity. We used optical topography (OT), a functional imaging technique based on near-infrared spectroscopy, to measure PFC activity for each participant in three experimental sessions repeated at 2-week intervals. In each session, the participants completed a self-report questionnaire of mood state and underwent OT measurement while performing verbal and spatial working memory (WM) tasks. The results showed that changes in the depressed-mood score between successive sessions were negatively correlated with those in the left PFC activation for the verbal WM task (ρ = -0.56, p < 0.05). In contrast, the PFC activation for the spatial WM task did not co-vary with participants' mood changes. We thus demonstrated that PFC activity during a verbal WM task varies depending on the participant's depressed mood state, independent of trait factors. This suggests that using optical topography to measure PFC activity during a verbal WM task can be used as a potential state marker for an individual's depressed mood state.     

强迫症患者言语流畅性任务脑激活时间特征的近红外光谱成像研究

目的:探讨强迫症患者言语流畅性任务(VFT)下前额叶及颞叶激活的时间特征。方法:选取70例符合DSM-IV强迫症诊断标准的患者和70例正常对照,应用52通道的近红外光谱成像技术(NIRS)测评完成VFT时前额叶及颞叶血流的变化。比较两组完成任务时氧合血红蛋白(oxy-Hb)、脱氧血红蛋白(deoxy-Hb)及总血红蛋白(total-Hb)浓度达峰时间的差异。结果:与正常对照组相比,强迫症患者52个通道oxy-Hb、deoxy-Hb和total-Hb浓度的平均达峰时间明显延迟[(61±12)s vs.(52±11)s,(64±10)s vs.(58±10)s,(59±13)s vs.(51±13)s,均P<0.01]。强迫症组oxy-Hb和total-Hb在眶额叶、额极、前额下回、颞中回及颞上回等脑区达峰时间明显延迟(均P<0.05,FDR校正)。结论:强迫症患者执行言语流畅性任务时前额叶及颞叶皮质激活可能有延迟。