Localizing the Language Network with fMRI and Functional Connectivity: Implications for Pre-Surgical Planning

Object: Functional MRI is frequently applied to lateralize language in pre-surgical planning, with potential to localize functionally important cortex too. Here we present BOLD signal activation maps and related functional connectivity, in response to three commonly administered fMRI language tasks. Methods: Datasets from 55 pre-surgical fMRI studies were analyzed. Verbal response naming, covert word generation and passive listening tasks were administered in all studies. Single-subject analyses, group analyses and region-of-interest analyses were conducted, and a multi-subject functional connectivity analysis was performed. Results: Single-subject analyses revealed that clinically important language regions were activated in all but three patients using the panel of tasks. Group analyses revealed significant bilateral BOLD signal increases in anterior and posterior language regions in response to verbal response naming and bilateral signal increase in posterior language regions only in response to passive listening. Covert word generation activated anterior language regions bilaterally and posterior language cortex in the dominant hemisphere. Functional connectivity analyses confirmed that activated regions were significantly correlated in all tasks. Conclusion: The findings of single-subject and group analyses add to the evidence supporting the use of a panel of fMRI tasks to map the language network for pre-surgical planning. Our findings support the additional use of functional connectivity analysis in routine language mapping to add to the localization value to fMRI. In addition, the results of our investigation demonstrate these three commonly applied tasks reliably activate unique aspects of the language network, which advocates closer individual inspection, guided by the surgical intervention planned.

Obstacles Facing the Implementation of Functional Magnetic Resonance Imaging （fMRI） of Brain in Jeddah City

fMRI （Functional Magnetic Resonance Imaging） is a relatively new technique that uses MRI （Magnetic Resonance Imaging） to measure the hemodynamic response （change in blood flow） related to neural activity in the brain. This paper aims to explore and identify the obstacles facing the implementation and applications of IMRI in radiology departments within Jeddah city by analyzing related data received by direct questionnaires and interviews with all the people working in MRI units in Jeddah city and finds that the major obstacle is lacking of awareness of fMRI among medical professionals and their training.

原发性失眠患者奖赏网络关键核团在静息态fMRI功能连接的改变

目的:利用功能性磁共振成像(fMRI)技术观察原发性患者奖赏网络区域中脑腹侧被盖(Ventral ttegmental area,VTA)以及伏隔核(Nucleus accumbens,NAcc)脑功能连接的改变。方法:28例原发性失眠比较26例健康对照组脑功能成像的改变,并分析中脑腹侧被盖以及伏隔核功能连接的改变与失眠的情绪障碍障碍之间的关系。结果:比较原发性失眠患者对比健康对照组,VTA与NAcc全脑的功能连接均降低,与VTA-l功能连接增降低的脑区为双侧前扣带回、左侧眶额回,与VTA-r功能连接增降低的脑区为双侧前扣带回、左侧眶额回、右侧中央前回,与NAcc-l功能连接降低的脑区为双侧丘脑、辅助运动区,与NAcc-r功能连接降低的脑区为双侧丘脑、小脑。结论:睡眠障碍会显著降低奖赏网络中VTA与NAcc的功能连接,说明长期睡眠障碍可能影响在原发性失眠患者奖赏处理能力,导致失眠患者情感功能发生障碍。

Acupuncture at Waiguan (TE5) influences activation/deactivation of functional brain areas in ischemic stroke patients and healthy people A functional MRI study

In the present study, 10 patients with ischemic stroke in the left hemisphere and six healthy controls were subjected to acupuncture at right Waiguan （TE5）. In ischemic stroke subjects, functional MRI showed enhanced activation in Broadmann areas 5, 6, 7, 18, 19, 24, 32, the hypothalamic inferior lobe, the mamiilary body, and the ventral posterolateral nucleus of the left hemisphere, and Broadmann areas 4, 6, 7, 18, 19 and 32 of the right hemisphere, but attenuated activation of Broadmann area 13, the hypothalamic inferior lobe, the posterior lobe of the tonsil of cerebellum, and the culmen of the anterior lobe of hypophysis, in the left hemisphere and Broadmann area 13 in the right hemisphere. In ischemic stroke subjects, a number of deactivated brain areas were enhanced, including Broadmann areas 6, 11,20, 22, 37, and 47, the culmen of the anterior lobe of hypophysis, alae lingulae cerebella, and the posterior lobe of the tonsil of cerebellum of the left hemisphere, and Broadmann areas 8, 37, 45 and 47, the culmen of the anterior lobe of hypophysis, pars tuberalis adenohypophyseos, inferior border of lentiform nucleus, lateral globus pallidus, inferior temporal gyrus, and the parahippocampal gyrus of the right hemisphere. These subjects also exhibited attenuation of a number of deactivated brain areas, including Broadmann area 7. These data suggest that acupuncture at Waiguan specifically alters brain function in regions associated with sensation, vision, and motion in ischemic stroke patients. By contrast, in normal individuals, acupuncture at Waiguan generally activates brain areas associated with insomnia and other functions.

基于模式识别的高水平运动员RS-fMRI数据分类研究

为弥补传统的广义线性模型(generalized linear model,GLM)方法的不足,并探索模式识别在运动脑科学当中的应用价值。使用支持向量机(support vector machine,SVM)模式识别算法,以低频振幅(fractional amplitude of low-frequency fluctuations,fALFF)、局部一致性(regional homogeneity,ReHo)和度中心度(degree centrality,DC)作为学习特征,对射击运动组和滑冰运动组(分类1)、射击运动组和对照组(分类2)以及速滑运动组和对照组(分类3)之间进行二分类,并计算每一个脑区在分类算法当中的权重。使用留一交叉验证法计算分类正确率,使用总的准确率、接受者操作特性曲线(receiver operating characteristic curve,ROC)、以及预测准确率来衡量机器分类算法的优劣性。结果表明:分类1中SVM算法的正确率较高且分类效果更稳定,总的准确率(total accuracy,tACC)可以维持在96.67%以上,曲线下面积(area under curve,AUC)均为1,说明SVM算法对区分不同项目运动员脑静息态功能特征时更有优势;在分类2和分类3中,SVM算法效果取决于使用的指标。其中,使用fALFF或者综合使用三个静息态指标的分类效果较稳定(tACC均在80%以上,AUC均在0.88以上);小脑在分类1算法中占较多的权重,提示不同运动项目运动员的脑功能活动之间差异最明显的部位主要在小脑上。而分类2和3中,除了小脑,还有一些与运动执行和控制及其他功能活动相关的脑区参与了算法的构成。通过SVM分类算法的应用获得较为理想的结果,展示了模式识别方法在运动科学领域的应用价值。研究成果有助于体育科学研究者从新的角度更加全面地理解运动与脑的关系。

Functional MRI activation of primary and secondary motor areas in healthy subjects

BACKGROUND： Functional MRI （fMRI） demonstrates the localization of hand representation in the motor cortex, thereby providing feasible noninvasive mapping of functional activities in the human brain. OBJECTIVE： To observe cortical activation within different cortical motor regions during repetitive hand movements in healthy subjects through the use of fMRI. DESIGN： An observational study, with each subject acting as his own control. SETTING： Department of Radiology, the First Affiliated Hospital of Nanchang University. PARTICIPANTS： Seven healthy volunteers, 4 males and 3 females, aged 19 to 38 years, participated in the study. All subjects were right-handed, with no neurological or psychological disorders. Informed written consent was obtained from all subjects, and the study was approved by the Institutional Review Board of the First Affiliated Hospital of Nanchang University. METHODS： The study was performed at the Department of Radiology between June-August 2005. A 1.5 Tesla Siemens MRI scanner （Symphony, Germany） was used to acquire T1-weighted structural images, which were oriented parallel to the line running through the anterior and the posterior commissures. Subjects were instructed on a task and were allowed to practice briefly prior to the imaging procedure. The motor activation task consisted of the right hand performing a clenching movement. The T1-W images were acquired from six alternating epochs of rest and activation from all seven healthy subjects. Data were collected with echoplanar imaging of brain oxygen level dependent （BOLD） sequence. Each series comprised six cycles of task performance （30 seconds）, alternating with rest （30 seconds） periods, and 3-second time intervals. The differences between active and baseline fMRI imaging were calculated using the student t-test. Differential maps were overlaid on the high resolution TI-W structural image for neuroanatomical correlation of activation areas. MAIN OUTCOME MEASURES： The omega-shaped hand knobs were recognized on T1-W structural images. Active signal changes in the primary （M1） and secondary motor （M2） areas, as well as the relationship between the hand knobs and M1 area activation, were analyzed. Region of interest was selected for signal change quantitative graphic analysis. RESULTS： All 7 enrolled volunteers were included in the final analysis. In the present study, hand knob structures were recognized on T1-weighted images in all subjects and were omega-shaped in the axial plane. Significant functional activations were observed in the contralateral primary motor area of all subjects. Activation signals were distributed mainly in the central sulcus around the hand knob. The contralateral primary sensory （S1） cortex was activated in most cases, and ipsilateral M1 was activated in 3 subjects. Contralateral or bilateral supplementary motor area （SMA） was also activated in 6 cases. Premotor area, or super parietal lobe, was activated in two subjects. Three-dimensional reconstruction demonstrated that the active signal of M1 was primarily located at the middle-lateral surface of the contralateral precentral gyrus in Brodman＇s area 4, and the signal of SMA activation was located in the mesial surface of the premotor area. CONCLUSION： The knob structure of the precentral gyrus is the representative motor area for hand movement. The cerebral cortical motor network was extensively activated during voluntary hand movements in normal subjects. In alert, conscious human subjects, the activated fMRI signal safely and non-invasively localized and lateralized the motor cortical activity associated with simple voluntary repetitive hand movements. Whether higher cognitive functions, such as perception and speech, can be similarly mapped using the fMRI technique and the BOLD method remains to be determined in future well-designed human studies.

Activated and deactivated functional brain areas in the Deqi state: A functional MRI study

We compared the activities of functional regions of the brain in the Deqi versus non-Deqi state, as reported by physicians and subjects cludng acupuncture, Twelve healthy volunteers received sham and true needling at the Waiguan （TE5） acupoint. Real-time cerebral functional MRI showed that compared with non-sensation after sham needling, true needling activated Brodmann areas 3, 6, 8, 9, 10, 11, 13, 20, 21, 37, 39, 40, 43, and 47, the head of the caudate nucleus, the parahippocampal gyrus, thalamus and red nucleus. True needling also deactivated Brodmann areas 1,2, 3, 4, 5, 6, 7, 9. 10. 18.24.31.40 and 46.

Effective doctor-patient communication skills training optimizes functional organization of intrinsic brain architecture:a restingstate functional MRI study

We studied the influence of doctor-patient communication skills training on brain functional architecture using resting-state functional MRI（rs-fMRI） with a regional homogeneity（ReHo） method. Ten medical students participated in the study. A 1-year long doctor-patient communication skills training program was conducted. RsfMRI data were collected at baseline, one month and one year after training. There was a significant increase in the communication skills test average scores between baseline and 1-month duration of training（P〈0.001）. After one month of communication skills training, medical students had decreased ReHo in the right superior temporal gyrus compared with the baseline. After one year of communication skills training, students had increased ReHo in multiple regions and decreased ReHo in several regions（P 〈0.05, Alphasim corrected）. The change of ReHo values in the superior temporal gyrus negatively correlated with the change of communication skills scale score between one month after communication skills training and baseline（r=-0.734, P= 0.036）. The training program we used can be an effective approach of improving doctor-patient communication skills, and the training resulted in functional plasticity of the brain’s architecture toward optimizing locally functional organization.

A central analgesic mechanism of acupuncture for migraine An ongoing functional MRI study

Shaoyang acupoints are the most frequently used in migraine treatment. However, the central anal- gesic mechanism remains poorly understood. Studies have demonstrated that single stimulus of the verum acupuncture in healthy subjects can induce significant connectivity or activity changes in pain- related central networks compared with sham acupuncture. However, these findings are not indicative of the central analgesic mechanism of acupuncture at Shaoyang acupoints. Thus, we recruited 100 migraine sufferers and randomly assigned them into five groups： Shaoyang uncommon acupoint, Shaoyang common acupoint, Yangming uncommon acupoint, non-acupoint control, and blank control groups. Subjects were subjected to evaluation of curative effects and functional MRI prior to and after 10 and 20 acupuncture treatments. All subjects were diagnosed by physicians and enrolled following clinical physical examination. Subjects were observed during 1-4 weeks after inclusion. At the fifth week, the first clinical evaluation and resting functional MRI were conducted. The Shaoyang uncom- mon acupoint, Shaoyang common acupoint, Yangming uncommon acupoint, and non-acupoint control grousp then were treated with acupuncture, five times per week, 20 times in total over 4 weeks. The second and third clinical evaluations and resting functional MRI screenings were conducted following 10 and 20 acupuncture treatments. The blank control group was observed during the 5 to 8 week pe- riod, followed by clinical evaluation and resting functional MRI. The aim of this study was to examine changes in brain functional activity and central networks in subjects with migraine undergoing acu- puncture at Shaoyang uncommon acupoints. This study provides a further explanation of the central analgesic mechanism by which acupuncture at Shaoyang acupoints treats migraine,

Nutritional Quality of Breakfast Affects Cognitive Function: An fMRI Study

To investigate the neural underpinnings of the effect of nutrition, brain activity of six young healthy volunteers who had a breakfast including various nutrients was compared to when they skipped breakfast or had only sugar for breakfast by functional magnetic resonance imaging. A repeated measure counterbalanced crossover design was employed. We demonstrated that significantly higher brain activation was observed in the medial aspect of the prefrontal cortex when the subjects had a nutritionally balanced breakfast while the subjects were conducting N-back tasks. This preliminary report was the first to demonstrate by means of brain imaging techniques that taking various nutrients as breakfast as well sugar has relevant impacts on underlying physiological events or cognition.

Global Functional Network Connectivity Disturbances in Parkinson’s Disease with Mild Cognitive Impairment by Resting-State Functional MRI

Examining the spontaneous BOLD activity to understand the neural mechanism of Parkinson’s disease(PD)with mild cognitive impairment(MCI)is a focus in resting-state functional MRI(rs-fMRI)studies.This study aimed to investigate the alteration of brain functional connectivity in PD with MCI in a systematical way at two levels:functional connectivity analysis within resting state networks(RSNs)and functional network connectivity(FNC)analysis.Using group independent component analysis(ICA)on rs-fMRI data acquired from 30 participants(14 healthy controls and 16 PD patients with MCI),16 RSNs were identified,and functional connectivity analysis within the RSNs and FNC analysis were carried out between groups.Compared to controls,patients with PD showed decreased functional connectivity within putamen network,thalamus network,cerebellar network,attention network,and self-referential network,and increased functional connectivity within execution network.Globally disturbed,mostly increased functional connectivity of FNC was observed in PD group,and insular network and execution network were the dominant network with extensively increased functional connectivity with other RSNs.Cerebellar network showed decreased functional connectivity with caudate network,insular network,and self-referential network.In general,decreased functional connectivity within RSNs and globally disturbed,mostly increased functional connectivity of FNC may be characteristics of PD.Increased functional connectivity within execution network may be an early marker of PD.The multi-perspective study based on RSNs may be a valuable means to assess functional changes corresponding to specific RSN,contributing to the understanding of the neural mechanism of PD.

Evaluating rehabilitation interventionsin Parkinson's disease with functional MRI:a promising neuroprotective strategy

Parkinson＇s disease （PD） is a progressive neurodegenerative disorder affecting approximately 10 million people world- wide （Planetta et al., 2014; Zigmond and Smeyne, 2014）. The principal clinical features of PD are bradykinesia, rigidity, tremor at rest and postural instability （Planetta et al., 2014）. It is known that both PD itself and the use of anti-parkinson drugs are associated with several non-motor symptoms such as cognitive impairment, neuropsychiatric disturbances and sleep, autonomic, and sensory disorders （Park and Stacy, 2009; Foster et al., 2014）. The histopathological hallmark of PD is the reduction of dopaminergic cells in the substantia nigra pars compacta, causing dopamine deficiency in spe- cific nuclei of the basal ganglia such as the dorsal striatum （Fearnley and Lees, 1991; Planetta et al., 2014）. The disrup- tion of the dopaminergic system has long been regarded as the major cause of PD; however, it has been shown that a widespread involvement of several non-dopaminergic path- ways also contribute to the clinical manifestations of PD （Park et al., 2014）.

The brain activation pattern of the medial temporal lobe during chewing gum: a functional MRI study

The human brain is known to be influenced by environmental stimuli（Feeney et al.,1982;Kaplan,1988）.Therefore,research on the brain activation pattern by external stimuli has been an important topic in neuroscience（Kaplan,1988）.Chewing gum has been known to have a positive effect on cognition,including alertness,attention,cognitive processing speed,

经颅磁电刺激治疗成人屈光参差性弱视的rs-fMRI机制研究

目的基于静息态功能磁共振成像(rs-fMRI)技术探讨经颅磁电刺激(TMS)干预对成人屈光参差性弱视患者关键脑区异常功能状态及损害特征的调控作用。方法纳入20例单(左)眼成人屈光参差性弱视患者,随机分为手术组[行后房型人工晶体(ICL)植入术]和TMS结合组(在手术组基础上进行TMS治疗),每组10例。两组患者在治疗前后均采用国际标准视力表检查视力以评价疗效。同时,两组患者分别在治疗前、治疗后进行1次rs-fMRI检查,采用局部一致性(ReHo)、低频振幅(ALFF)、比率低频振幅(fALFF)3种算法对获取的rs-fMRI图像进行脑区功能状态及响应特征分析。结果与治疗前相比,治疗后两组患者的裸眼视力均显著提高,且显著高于治疗前矫正视力(均P<0.05);治疗后两组相比,TMS结合组裸眼视力改善程度优于手术组(P<0.05)。手术组、TMS结合组治疗前后ReHo、fALFF值均无差异;与治疗前相比,手术组治疗后同侧额叶ALFF值升高,TMS结合组治疗后同侧小脑ALFF值降低;与手术组相比,TMS结合组治疗后同侧额叶、额上回ReHo值降低,对侧颞叶、颞上回ALFF值降低,对侧枕叶、楔叶fALFF升高(均P<0.05)。结论手术组和TMS结合组成人屈光参差性弱视患者的脑区自发活动改善效果显著。ICL植入术可能通过激活同侧额叶发挥作用;ICL植入术结合TMS治疗可能通过改善小脑功能,提高对侧枕叶、楔叶的兴奋性,调节枕叶相邻皮质及其他视觉相关皮质(同侧额叶及对侧颞叶)的神经元功能活动,纠正患者两眼间的兴奋性差异而发挥作用。

A review of functional MRI application for brain research of Chinese language processing

As one of the most widely used languages in the world,Chinese language is distinct from most western languages in many properties,thus providing a unique opportunity for understanding the brain basis of human language and cognition.In recent years,non-invasive neuroimaging techniques such as magnetic resonance imaging(MRI)blaze a new trail to comprehensively study specific neural correlates of Chinese language processing and Chinese speakers.We reviewed the application of functional MRI(fMRI)in such studies and some essential findings on brain systems in processing Chinese.Specifically,for example,the application of task fMRI and resting-state fMRI in observing the process of reading and writing the logographic characters and producing or listening to the tonal speech.Elementary cognitive neuroscience and several potential research directions around brain and Chinese language were discussed,which may be informative for future research.

Acupoints combination correlates with activation of cerebral areas A functional MRI study

Acupoint combination is a method used for acupoint treatment of patients. Traditionally, acupoints are matched along the meridian distribution, which is a common rule in clinical practice, but the underlying mechanism remains unclear. Cerebral scans with functional magnetic resonance imaging （fMRI） have been used in the study of acupuncture and acupoint specifically. In this study, fMRI was used to detect the activation of the brain areas under different acupoints, matched along different meridians, to elucidate the acupoint combination via a modern medical approach. Forty healthy volunteers were randomly divided into the following groups： Waiguan point （SJ 5）, Waiguan （SJ 5） ＋ Zhigou （SJ 6） （2 acupoints come from the same meridian）, Waiguan （SJ 5） ＋ Neiguan （PC 6） （2 acupoints come from 2 meridians with the relationship of interior-exterior）, Waiguan （SJ 5） ＋ Yanglingquan （GB 34） （2 acupoints come from 2 meridians with the same name-Shaoyang Meridian）, and sham point groups （needling in different points on the right hand）. A real-time cerebral fMRI scan was simultaneously performed. The cerebral activation rate, and the number and strength of different regions of interest were compared among the groups. The fMRI cerebral imaging confirmed that there were some differences in the activation of cerebral areas by the needlings in SJ 5, and in combination with other acupoints. Needling at SJ 5 alone greatly activated the right cerebellum, while needling at both SJ 5 and different co-needling points activated different cerebral functional areas.

Processing Chinese hand-radicals activates the medial frontal gyrus A functional MRI investigation

Embodied semantics theory asserts that the meaning of action-related words is neurally represented through networks that overlap with or are identical to networks involved in sensory-motor processing. While some studies supporting this theory have focused on Chinese characters, less attention has been paid to their semantic radicals. Indeed, there is still disagreement about whether these radicals are processed independently. The present study investigated whether radicals are processed separately and, if so, whether this processing occurs in sensory-motor regions. Materials consisted of 72 high-frequency Chinese characters, with 18 in each of four categories： hand-action verbs with and without hand-radicals, and verbs not related to hand actions, with and without hand-radicals. Twenty-eight participants underwent functional MRI scans while reading the characters. Compared to characters without hand-radicals, reading characters with hand-radicals activated the right medial frontal gyrus. Verbs involving hand-action activated the left inferior parietal lobule, possibly reflecting integration of information in the radical with the semantic meaning of the verb. The findings may be consistent with embodied semantics theory and suggest that neural representation of radicals is indispensable in processing Chinese characters.

Effects of visual information regarding tactile stimulation on the somatosensory cortical activation：a functional MRI study

Many studies have investigated the evidence for tactile and visual interactive responses to activation of various brain regions.However,few studies have reported on the effects of visuo-tactile multisensory integration on the amount of brain activation on the somatosensory cortical regions.The aim of this study was to examine whether coincidental information obtained by tactile stimulation can affect the somatosensory cortical activation using functional MRI.Ten right-handed healthy subjects were recruited for this study.Two tasks（tactile stimulation and visuotactile stimulation）were performed using a block paradigm during f MRI scanning.In the tactile stimulation task,in subjects with eyes closed,tactile stimulation was applied on the dorsum of the right hand,corresponding to the proximal to distal directions,using a rubber brush.In the visuotactile stimulation task,tactile stimulation was applied to observe the attached mirror in the MRI chamber reflecting their hands being touched with the brush.In the result of SPM group analysis,we found brain activation on the somatosensory cortical area.Tactile stimulation task induced brain activations in the left primary sensory-motor cortex（SM1）and secondary somatosensory cortex（S2）.In the visuo-tactile stimulation task,brain activations were observed in the both SM1,both S2,and right posterior parietal cortex.In all tasks,the peak activation was detected in the contralateral SM1.We examined the effects of visuo-tactile multisensory integration on the SM1 and found that visual information during tactile stimulation could enhance activations on SM1 compared to the tactile unisensory stimulation.

Peri-infarct reorganization at the centrum semiovale and corona radiata A diffusion tensor tractography and functional MRI study

Peri-infarct reorganization has been reported in stroke patients with a lesion at the cerebral cortex, corona radiata, or pons, separately. However, there have been no reports describing the patients with peri-infarct reorganization at multiple levels. The present study reported a patient with a middle cerebral artery infarct who showed complete paralysis of the right extremities at stroke onset. Results showed that at 3 years after stroke onset, patient＇s motor function of the affected hand appeared to have been recovered by the motor tract, which reorganized into the anterior areas of the infarcted centrum semiovale and corona radiata, as demonstrated by diffusion tensor tractography study analyzed using functional MRI activation results. This result indicates that the human brain can show extensive brain plasticity and that saving the adjacent area or penumbra around the infarct even though the lesion from multiple levels is important for functional recovery after stroke.

Effects of task orientation on subsequent source memory as revealed by functional MRI

Episodic memories are composed of various interrelated elements, including those specific to items of central interest and those pertaining to related features, such as the color, shape, size, spatial location, temporal order, and media or modalities of presentation. Memory about a core item （such as a word, object, or picture） is called item memory while memory about the context or related fea- tures of a core item is defined as source memory. What determines which sources within an episode are successfully remembered is of particular interest to researchers. Behavioral evidence suggests that the orientation of a memory task influences whether the related source of the item will be re- membered later. This study explored changes in the hippocampus and prefrontal cortex while par- ticipants completed two tasks： an item-oriented task and a source-oriented task. We used functional MRI to investigate the neural mechanisms by which task orientation influences source encoding. We found that subsequent source memory effects in the right prefrontal cortex and hippocampus were modulated by task orientation, whereas task orientation modulated item memory effects in the prefrontal cortex. These findings highlight the possibility that the hippocampus contributes to the intentional encoding of item-source associations, whereas the prefrontal cortex is biased toward processing information to which attention is directed.