Cortical connections of the inferior parietal cortical convexity of the macaque monkey

We traced the cortical connections of the 4 cytoarchitectonic fields--Opt, PG, PFG, PF--forming the cortical convexity of the macaque inferior parietal lobule (IPL). Each of these fields displayed markedly distinct sets of connections. Although Opt and PG are both targets of dorsal visual stream and temporal visual areas, PG is also target of somatosensory and auditory areas. Primary parietal and frontal connections of Opt include area PGm and eye-related areas. In contrast, major parietal and frontal connections of PG include IPL, caudal superior parietal lobule (SPL), and agranular frontal arm-related areas. PFG is target of somatosensory areas and also of the medial superior temporal area (MST) and temporal visual areas and is connected with IPL, rostral SPL, and ventral premotor arm- and face-related areas. Finally, PF is primarily connected with somatosensory areas and with parietal and frontal face- and arm-related areas. The present data challenge the bipartite subdivision of the IPL convexity into a caudal and a rostral area (7a and 7b, respectively) and provide a new anatomical frame of reference of the macaque IPL convexity that advances our present knowledge on the functional organization of this cortical sector, giving new insight into its possible role in space perception and motor control.     

Role of parietal cortex and hippocampus in representing spatial information.

Rats with lesions in the parietal cortex or hippocampus as well as cortical lesion and sham-operated controls were tested for acquisition or retention of a cheese board spatial task (dry land version of a water maze task). Results indicated that, relative to controls, rats with hippocampal or parietal cortex lesions were impaired in both acquisition and retention of the spatial task as measured by increased distances traveled to find the correct food location. It is suggested that both the hippocampus and parietal cortex subserve spatial representations required for optimal learning and performance of the cheese board spatial task.     

Real and illusory contour processing in area V1 of the primate: a cortical balancing act.

It is known that neurons in area V2 (the second visual area) can signal the orientation of illusory contours in the primate. Whether area V1 (primary visual cortex) can signal illusory contour orientation is more controversial. While some electrophysiology studies have ruled out illusory signaling in V1, other reports suggest that V1 shows some illusory-specific response. Here, using optical imaging and single unit electrophysiology, we report that primate V1 does show an orientation-specific response to the 'abutting line grating' illusory contour. However, this response does not signal an illusory contour in the conventional sense. Rather, we find that illusory contour stimulation leads to an activation map that, after appropriate subtraction of real line signal, is inversely related to the real orientation map. The illusory contour orientation is thus negatively signaled or de-emphasized in V1. This 'activation reversal' is robust, is not due merely to presence of line ends, is not dependent on inducer orientation, and is not due to precise position of line end stimulation of V1 cells. These data suggest a resolution for previous apparently contradictory experimental findings. We propose that the de-emphasis of illusory contour orientation in V1 may be an important signal of contour identity and may, together with illusory signal from V2, provide a unique signature for illusory contour representation.     

颞肌、颞筋膜、颅骨骨膜复合组织瓣转位悬吊法矫治晚期面瘫

目的 探讨矫治晚期面瘫简单有效的动力性矫正手术方式.方法 将颞肌、颞筋膜瓣转位悬吊法作了如下三方面的改进：①利用颅顶部骨膜使颞肌、颞肌筋膜瓣得到适当延长和张力加强.②升高颞肌颞筋膜瓣转位下翻的平面.③采用硅胶丰颞片填充颞部供瓣区凹陷.结果 克服了原术式供瓣长度不足的缺陷,并获得了一条在组织结构上相延续的完整的颞肌、颞筋膜、颅骨骨膜复合组织瓣供转位修复,而且有效地避免了颞部供瓣区的凹陷畸形,较大程度地改善了术后颧部臃肿的外观.结论 改良后的术式成功地避免了原术式的不足,获得了较好的动力性矫治效果.     

The laminar pattern of connections between prefrontal and anterior temporal cortices in the Rhesus monkey is related to cortical structure and function

The laminar pattern of axonal termination from prefrontal (caudal orbitofrontal, rostral orbitofrontal and lateral areas) to anterior temporal areas (entorhinal cortex, perirhinal cortex and area TE) and from temporal to prefrontal areas was investigated with the aid of anterograde tracers. Both regions are characterized by structural heterogeneity, and include agranular, dysgranular and granular cortical types, denoting, respectively, the absence, incipience and presence of granular layer 4. In addition, both the prefrontal and anterior temporal cortices are composed of areas that have related though specialized functions. The pattern of cortical axonal termination was associated with both the structural type of the cortex of origin and the structure of the destination cortex. Thus, efferent fibers from a single origin in either prefrontal or anterior temporal cortex terminated in different patterns depending on their target area. Conversely, axons terminated in different patterns in a single target area, prefrontal or anterior temporal, depending on their area of origin. Projections from agranular or dysgranular type cortices (e.g. medial temporal areas and caudal orbitofrontal areas) terminated mostly in the upper layers of granular cortices (e.g. area TE and lateral prefrontal areas), and projections from granular cortices terminated mostly in the deep layers of agranular or dys- granular cortices. A robust projection from dysgranular orbitofrontal areas terminated in the deep layers of the agranular entorhinal cortex. Projections from prefrontal areas to area TE terminated in the upper layers, and may facilitate focused attention on behaviorally relevant stimuli processed through reciprocal pathways between prefrontal and temporal cortices.     

Sevoflurane modulates both GABAA and GABAB receptors in area CA1 of rat hippocampus

It has been suggested that volatile anaesthetics enhance synaptic inhibition via gamma-aminobutyric acid (GABA) in the central nervous system. We have examined the effects of sevoflurane on GABAA and GABAB receptors in rat hippocampus in vitro. Extracellular recordings were used to record field potentials in rat CA1 pyramidal neurones of transverse hippocampal slices, stimulated electrically via stratum radiatum input. Sevoflurane 0.4-5.0 vol% decreased the amplitudes of population spikes (PS) of CA1 neurones in a concentration-dependent (calculated ED50 = 6.31 vol%) and reversible manner. The GABAA antagonist, bicuculline methiodide 5 x 10(-5) mol litre-1, induced oscillations (multiple spikes) and blocked the inhibitory actions of sevoflurane in the initial component (up to 24.8 ms) of the oscillation. The latter portion of the oscillation (greater than 24.8 ms) was depressed by sevoflurane. The GABAB antagonist, phaclofen 5 x 10(-4) mol litre-1 partially blocked the effects of sevoflurane on the latter portion of the bicuculline-induced oscillation. Sevoflurane 2.0 vol% significantly enhanced paired-pulse (PS2/PS1) facilitation (from 128.4% to 155.5% at an inter-stimulus interval of 37.9 ms); this enhancement was blocked by phaclofen. Stimulus-response relationships revealed that 2.0 vol% sevoflurane increased the intensity of threshold for PS generation to 109.8% of control. Both the GABAA agonist, muscimol 2 x 10(-5) mol litre-1 and the GABAB agonist, (+/-)-baclofen 10(-5) mol litre-1, potentiated the effects of sevoflurane. Sevoflurane enhanced thresholds by 137.1% and 138.5% of control in the presence of muscimol and (+/-)-baclofen, respectively. The results demonstrate that sevoflurane at clinical concentrations activated both GABAA- and GABAB- mediated inhibitions in area CA1 of the hippocampus, and that sevoflurane and GABA agonists (muscimol and baclofen) acted on different domains on the GABAA and GABAB receptors, respectively.      

丙泊酚对大鼠离体海马CA1区场电位的作用

目的观察临床常用的静脉麻醉药丙泊酚对大鼠离体完整海马CA1区场电位不同振荡频段的作用,探讨丙泊酚对海马内部神经环路功能可能产生的影响。方法选择出生后14～16 d雄性SD大鼠于4℃条件下进行完整海马的剥离。待孵育1～2 h稳定后,移至电生理记录槽。实验根据灌流的丙泊酚浓度不同分为对照组(C组)、丙泊酚1μmol/L组(P_1组)、丙泊酚20μmol/L组(P_(20)组)、丙泊酚40μmol/L组(P_(40)组)和丙泊酚80μmol/L组(P_(80)组)。C组不予丙泊酚灌流,为基础值,P_1组、P_(20)组、P_(40)组和P_(80)组分别给予丙泊酚1、20、40和80μmol/L灌流,采用玻璃微电极记录离体完整海马CA1区辐射层的场电位信号,进行场电位的功率谱强度分析。将C组的基础值设定为1,分别计算并比较P_1组、P_(20)组、P_(40)组和P_(80)组离体完整海马CA1区场电位不同振荡频段(δ:1～4 Hz,θ:4～8 Hz,α:8～13 Hz,β:13～30 Hz,γ:30～80 Hz)与C组比值。结果与C组比较,P_1组场电位θ频段明显增强(P0.05),γ频段明显减弱(P0.05),P_(20)组、P_(40)组和P_(80)组场电位不同振荡频段均明显减弱(P0.05)。与P_1组比较,P_(20)组场电位δ、θ、α、β频段明显减弱(P0.05),P_(40)组和P_(80)组场电位不同振荡频段均明显减弱(P0.05)。与P_(20)组比较,P_(80)组场电位δ、θ、α频段明显减弱(P0.05)。与P_(40)组比较,P_(80)组场电位δ频段明显减弱(P0.05)。结论除θ频段外,丙泊酚对海马CA1区场电位的δ、α、β和γ频段呈现浓度依赖的抑制作用;对于θ频段,大于20μmol/L浓度的丙泊酚仍然表现为抑制作用,但在1μmol/L浓度下却表现为增强作用,显示低浓度丙泊酚对海马内部神经环路可能存在兴奋作用。     

Differential effects of aging and insulin-like growth factor-1 on synapses in CA1 of rat hippocampus

Aging-related impairments of learning and memory can be ameliorated by 28 days of intracerebroventricular (icv) infusion of insulin-like growth factor-1 (IGF-1) in old rats. The present study investigated whether there is an aging-related synaptic decline in the stratum radiatum of hippocampal CA1 and whether IGF-1 can ameliorate that decline. Five young (4 months), five middle-aged (18 months) and five old (29 months) Fischer 344xBrown Norway rats received saline infusion; five old (29 months) rats received IGF-1 infusion for 28 days preceding sacrifice. Pyramidal neurons, total synaptic profiles as well as synaptic profiles in multiple spine bouton (MSB) complexes in CA1 were quantified stereologically with the physical disector technique and the postsynaptic density (PSD) length was determined as well. The results indicated a decrease of total synapses between middle and old age but a maintenance of PSD length and MSB synapses throughout life. IGF-1 infusion in old rats did not reverse the aging-related decline in total synapses but did increase PSD length and the number of MSB synapses. These changes in synaptic configurations are morphological correlates of enhanced synaptic efficacy. Thus, aging and IGF-1 affect different, but complementary, aspects of synapses in hippocampal CA1.     

From perception to action: temporal integrative functions of prefrontal and parietal neurons.

The dorsolateral prefrontal cortex (DPFC) and the posterior parietal cortex (PPC) are anatomically and functionally interconnected, and have been implicated in working memory and the preparation for behavioral action. To substantiate those functions at the neuronal level, we designed a visuomotor task that dissociated the perceptual and executive aspects of the perception-action cycle in both space and time. In that task, the trial-initiating cue (a color) indicated with different degrees of certainty the direction of the correct manual response 12 s later. We recorded extracellular activity from 258 prefrontal and 223 parietal units in two monkeys performing the task. In the DPFC, some units (memory cells) were attuned to the color of the cue, independent of the response-direction it connoted. Their discharge tended to diminish in the course of the delay between cue and response. In contrast, few color-related units were found in PPC, and these did not show decreasing patterns of delay activity. Other units in both cortices (set cells) were attuned to response-direction and tended to accelerate their firing in anticipation of the response and in proportion to the predictability of its direction. A third group of units was related to the determinacy of the act; their firing was attuned to the certainty with which the animal could predict the correct response, whatever its direction. Cells of the three types were found closely intermingled histologically. These findings further support and define the role of DPFC in executive functions and in the temporal closure of the perception-action cycle. The findings also agree with the involvement of PPC in spatial aspects of visuomotor behavior, and add a temporal integrative dimension to that involvement. Together, the results provide physiological evidence for the role of a prefrontal-parietal network in the integration of perception with action across time.     

The functional organization and cortical connections of motor cortex in squirrels

Despite extraordinary diversity in the rodent order, studies of motor cortex have been limited to only 2 species, rats and mice. Here, we examine the topographic organization of motor cortex in the Eastern gray squirrel (Sciurus carolinensis) and cortical connections of motor cortex in the California ground squirrel (Spermophilus beecheyi). We distinguish a primary motor area, M1, based on intracortical microstimulation (ICMS), myeloarchitecture, and patterns of connectivity. A sensorimotor area between M1 and the primary somatosensory area, S1, was also distinguished based on connections, functional organization, and myeloarchitecture. We term this field 3a based on similarities with area 3a in nonrodent mammals. Movements are evoked with ICMS in both M1 and 3a in a roughly somatotopic pattern. Connections of 3a and M1 are distinct and suggest the presence of a third far rostral field, termed "F," possibly involved in motor processing based on its connections. We hypothesize that 3a is homologous to the dysgranular zone (DZ) in S1 of rats and mice. Our results demonstrate that squirrels have both similar and unique features of M1 organization compared with those described in rats and mice, and that changes in 3a/DZ borders appear to have occurred in both lineages.     

Exacerbation of cortical and hippocampal CA1 damage due to posttraumatic hypoxia following moderate fluid-percussion brain injury in rats.

OBJECT: Patients with head injuries often experience respiratory distress that results in a secondary hypoxic insult. The present experiment was designed to assess the histopathological consequences of a secondary hypoxic insult by using an established rodent model of traumatic brain injury (TBI). METHODS: Intubated anesthetized rats were subjected to moderate (1.94-2.18 atm) parasagittal fluid-percussion injury (FPI) to the brain. Following the TBI, the animals were maintained for 30 minutes by using either hypoxic (TBI-HY group, nine animals) or normoxic (TBI-NO, 10 animals) gas levels. Sham-operated animals also underwent all manipulations except for the FPI (sham-HY group, seven animals; and sham-NO group, seven animals). Three days after TBI the rats were killed, and quantitative histopathological evaluation was undertaken. Cortical contusion volumes were dramatically increased in the TBI-HY group compared with the TBI-NO group (p < 0.03). Qualitative assessment of cortical and subcortical structures demonstrated significant damage within the hippocampal areas, CA1 and CA2, of TBI-HY animals compared with the TBI-NO animals (both p < 0.03). There was also a significant increase in the frequency of damaged neuronal profiles within the middle and medial sectors of the CA1 hippocampus (p < 0.03) due to the hypoxic insult. CONCLUSIONS: The results of this study demonstrate that a secondary hypoxic insult following parasagittal FPI exacerbates contusion and neuronal pathological conditions. These findings emphasize the need to control for secondary hypoxic insults after experimental and human head injury.     

Extracellular magnesium ion modifies the actions of volatile anesthetics in area CA1 of rat hippocampus in vitro

BACKGROUND: Magnesium ion (Mg2+) is involved in important processes as modulation of ion channels, receptors, neurotransmitter release, and cell excitability in the central nervous system. Although extracellular Mg2+ concentration ([Mg2+]o) can be altered during general anesthesia, there has been no evidence for [Mg2+]o-dependent modification of anesthetic actions on neural excitability in central nervous system preparations. The purpose of current study was to determine whether the effects of volatile anesthetics are [Mg2+]o-dependent in mammalian central nervous system. METHODS: Extracellular electrophysiologic recordings from CA1 neurons in rat hippocampal slices were used to investigate the effects of [Mg2+]o and anesthetics on population spike amplitude and excitatory postsynaptic potential slope. RESULTS: The depression of population spike amplitudes and excitatory postsynaptic potential slopes by volatile anesthetics were significantly dependent on [Mg2+]o. The effects were attenuated in the presence of a constant [Mg2+]o/extracellular Ca2+ concentration ratio. However, neither N-methyl-d-aspartate receptor antagonists nor a non-N-methyl-d-aspartate receptor antagonist altered the [Mg2+]o-dependent anesthetic-induced depression of population spikes. Volatile anesthetics produced minimal effects on input-output (excitatory postsynaptic potential-population spike) relations or the threshold for population spike generation. The effects were not modified by changes in [Mg2+]o. In addition, the population spike amplitudes, elicited via antidromic (nonsynaptic) stimulation, were not influenced by [Mg2+]o in the presence of volatile anesthetics. CONCLUSIONS: These results provide support that alteration of [Mg2+]o modifies the actions of volatile anesthetics on synaptic transmission and that the effects could be, at least in part, a result of presynaptic Ca2+ channel-related mechanisms.     

硫喷妥钠对大鼠海马CA1区锥体神经元GABAA受体的作用

目的 研究硫喷妥钠（Ｔｈ）对急性急性大鼠海马ＣＡ１区锥体神经元γ－氨基丁酸Ａ型（ＧＡＢＡＡ）受体的作用。方法 采用制霉菌素穿乳膜片钳技术。结果 Ｔｈ呈浓度依赖地直接激发内向电流（ＩＴｈ）,其翻转电位与ＣＩ＾－理论平衡电位接近,ＩＴｈ可被ＧＡＢＡＡ受体拮抗剂荷包牡丹碱（ＢＩＣ）阻断;Ｔｈ增强ＧＡＢＡ诱发的内向电流（ＩＣＡＢＡ）,使ＧＡＢＡ浓度效应曲线平行左移。结论 Ｔｈ既能直接激活ＧＡＢＡＡ受体又能     

中低温体外循环对大鼠海马CA1区神经元凋亡的影响

目的 观察中低温体外循环(CPB)对大鼠海马CA1区神经元凋亡的影响及机制。方法 雄性SD大鼠27只,随机分为三组:CPB后1h组(n=6)、CPB后6h组(n=6)及假手术组(Sham组,n=5)。所有动物在咪唑安定、芬太尼麻醉后经口插管控制呼吸,置入颈静脉流出管和尾动脉输入管,肝素抗凝(500μ/kg)。CPB组采用中低温CPB(26～28℃),经尾动脉灌注、颈静脉右心房-腔静脉引流,灌流量160ml·kg~(-1)·min~(-1),总转流时间2h,Sham组操作同CPB术后1h组,但不经历CPB,三组持续监测动脉压、ECG及动脉血气。CPB后1h组、CPB后6h组分别在术后1、6h时处死大鼠,4％多聚甲醛灌注固定后取大脑组织,TUNEL法检测神经元凋亡,并用电子显微镜观察神经元超微结构变化,用免疫组化法检测海马CA1区神经元bax和bcl-2蛋白表达。结果 与Sham组比较,CPB后1h组bax和bcl-2蛋白表达增强,CPB后6h组bax表达增强、bcl-2蛋白表达减弱(P<0.05);与CPB后1h组比较,CPB后6h组bax表达增强、bcl-2蛋白表达减弱(P<0.05)。与Sham组比较,CPB后1h、CPB后6h组bax/bcl-2比值、神经元凋亡率升高,CPB后6h组bax/bcl-2比值、神经元凋亡率高于CPB后1h组(P<0.05)。电镜下CPB后1h组海马CA1区神经元部分线粒体肿胀、空泡变性、嵴减少或消失;CPB后6h组可见少量神经元变性固缩、核不规则、核     

Electrophysiological connections between the hippocampus and entorhinal cortex in patients with complex partial seizures

The electrophysiological properties of the neural pathways between the hippocampus and the entorhinal cortex were studied intraoperatively in 31 patients undergoing anterior temporal lobectomy for medically intractable complex partial seizures. The hippocampus, removed en bloc, was studied histologically and the pathology was correlated with the electrophysiological findings. In 29 of the patients, entorhinal stimulation evoked a characteristic positive-negative potential in the hippocampus. The entorhinal-evoked hippocampal response closely resembled, or was identical to, the spontaneously occurring hippocampal interictal spike discharge. In patients with Ammon's horn sclerosis in whom there was a major loss of neurons in the hippocampal subfields CA1, CA3, and CA4, the evoked responses were of simple morphology and long latency (mean 21.9 msec to the peak of the first potential). In patients with a ganglioglioma in whom the hippocampus was histologically normal, the evoked responses were of greater complexity and shorter latency (mean 11.8 msec). Stimulation at a single entorhinal site evoked similar waveforms at different hippocampal recording sites. Conversely, stimulation at different entorhinal sites evoked similar responses at a single hippocampal recording site. Stimulation of the hippocampus evoked a potential in the entorhinal cortex and, in some instances, in the amygdala, insula, and lateral temporal cortex. These connections may produce a positive feedback loop that favors seizure generation.     

Effects of low-power laser irradiation on the threshold of electrically induced paroxysmal discharge in rabbit hippocampus CA1

In acute experiments using adult rabbits, we measured the paroxysmal discharge threshold (PADT) elicited by stimulation to the apical dendritic layer of the hippocampal CA1 region before and after low-power laser irradiation. Nd:YVO₄ laser irradiation (wavelength: 532 nm) was introduced into the same region as the stimulation site. The average PADT was 247?±?13 μA (n?=?18) before laser irradiation, while after 5-min laser irradiation with 50, 75, and 100 mW, PADT was 333?±?40 (n?=?4), 353?±?33 (n?=?4) and 367?±?27 μA (n?=?6), respectively. The latter two increments were statistically significant compared to the control (p?<?0.05 and p?<?0.01). After 10-min laser irradiation with 75 and 100 mW, PADT was 340?±?47 (n?=?9) and 480?±?60 μA (n?=?11; p?<?0.01), respectively. Laser irradiation with a specific wavelength and average power offers the potential to suppress the generation of paroxysmal discharges in rabbit hippocampus CA1. Correlation analyses suggest that PADT increments are based on photochemical as well as photothermal effects of laser irradiation.     

Functional organization of temporal frequency selectivity in primate visual cortex

Several studies have shown that neurons with similar response properties are arranged together in domains across primary visual cortex (V1). An orderly pattern of domains has been described for preferences to ocular dominance, orientation, and spatial frequency. Temporal frequency preference, another important attribute of the visual scene, also might be expected to map into different domains. Using optical imaging and a variety of quantitative methods, we examined how temporal frequency selectivity is mapped in V1 of the prosimian primate, bush baby (Otolemur garnetti). We found that unlike other attribute maps, selectivity for different temporal frequencies is arranged uniformly across V1 with no evidence of local clustering. Global tuning for temporal frequency, based on magnitude of response, showed a good match to previous tuning curves for single neurons. A peak response was found around 2.0 Hz, with smaller attenuation at lower temporal frequencies than at higher frequencies. We also examined whether the peak temporal frequency response differed between anatomical compartments defined by cytochrome oxidase (CO). No significant differences in the preference for temporal frequency were found between these CO compartments. Our findings show that key sensory attributes that are linked in perception can be organized in quite distinct ways in V1 of primates.     

Synchronization between temporal and parietal cortex during multimodal object processing in man

A series of recordings in cat visual cortex suggest that synchronous activity in neuronal cell ensembles serves to bind the different perceptual qualities belonging to one object. We provide evidence that similar mechanisms seem also to be observable in human subjects for the representation of supramodal entities. Electroencephalogram (EEG) was recorded from 19 scalp electrodes (10/20 system) in 19 human subjects and EEG amplitude and coherence were determined during presentation of objects such as house, tree, ball. Objects were presented in three different ways: in a pictorial presentation, as spoken words and as written words. In order to find correlates of modality-independent processing, we searched for patterns of activation common to all three modalities of presentation. The common pattern turned out to be an increase of coherence between temporal and parietal electrodes in the 13-18 Hz beta1 frequency range. This is evidence that population activity of temporal cortex and parietal cortex shows enhanced coherence during presentation of semantic entities. Coherent activity in this low-frequency range might play a role for binding of multimodal ensembles.