共查询到20条相似文献,搜索用时 15 毫秒
1.
Bringoux L Robic G Gauthier GM Vercher JL 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,185(4):673-680
Previous studies have shown that the perception of the earth-based visual horizon, also named Gravity Referenced Eye Level
(GREL), is modified by body tilt around a trans-ocular axis. Here, we investigated whether estimates of the elevation of a
luminous horizontal line presented on a screen in otherwise darkness and estimates of the possibility of passing under are
identically related to body tilt in absence of motion. Results showed that subjects overestimated the elevation of the projected
line, whatever their body orientation. In the same way, subjects also overestimated their capacity of passing under the line.
Both estimates appeared as a linear function of body tilt, that is, forward body tilt yielded increased overestimations, and
backward body tilt yielded decreased overestimations. More strikingly, the linear effect of body tilt upon these estimates
is comparable to that previously observed for direct GREL judgements. Overall, these data strongly suggest that the perception
of the elevation of a visible obstacle and the perception of the ability of passing under in otherwise darkness shared common
processes which are intimately linked to the GREL perception. The effect of body tilt upon these perceptions may illustrate
an egocentric influence upon the semi-geocentric frame of reference required to perform the task. Possible interactions between
egocentric and geocentric frames of reference are discussed. 相似文献
2.
Steele-Russell I Russell MI Castiglioni JA Setlow B Werka T 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,188(2):199-213
In an earlier experiment we showed that selective attention plays a critical role in rabbit eye blink conditioning (Steele-Russell
et al. in Exp Brain Res 173:587–602, 2006). The present experiments are concerned to examine the extent to which visual recognition processes are a separate component
from the motor learning that is also involved in conditioning. This was achieved by midline section of the optic chiasma which
disconnected the direct retinal projections via the brainstem to the cerebellar oculomotor control system. By comparing both
normal and chiasma-sectioned rabbits it was possible to determine the dependence or independence of conditioning on the motor
expression of the eye blink response during training. Both normal and chiasma-sectioned animals were tested using a multiple
test battery to determine the effect of this redirection of the visual input pathways on conditioning. All animals were first
tested for any impairment in visual capability following section of the optic chiasma. Despite the loss of 90% of retinal
ganglion cell fibres, no visual impairment for either intensity or pattern vision was seen in the chiasma animals. Also no
difference was seen in nictitating membrane (NM) conditioning to an auditory signal between normal and chiasma animals. Testing
for motor learning to a visual signal, the chiasma rabbits showed a complete lack of any NM conditioning. However the sensory
tests of visual conditioning showed that chiasma-sectioned animals had completely normal sensory recognition learning. These
results show that NM Pavlovian conditioning involves anatomically separate and independent sensory recognition and motor output
components of the learning.
This research was supported by S&W research grants ID# 1810 to ISR and ID# 7985 to JAC. 相似文献
3.
Goal-directed reaching: movement strategies influence the weighting of allocentric and egocentric visual cues 总被引:3,自引:2,他引:1
Neely KA Tessmer A Binsted G Heath M 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,186(3):375-384
The location of an object in peripersonal space can be represented with respect to our body (i.e., egocentric frame of reference)
or relative to contextual features and other objects (i.e., allocentric frame of reference). In the current study, we sought
to determine whether the frame, or frames, of visual reference supporting motor output is influenced by reach trajectories
structured to maximize visual feedback utilization (i.e., controlled online) or structured largely in advance of movement
onset via central planning mechanisms (i.e., controlled offline). Reaches were directed to a target embedded in a pictorial
illusion (the induced Roelofs effect: IRE) and advanced knowledge of visual feedback was manipulated to influence the nature
of reaching control as reported by Zelaznik et al. (J Mot Behav 15:217–236, 1983). When vision could not be predicted in advance of movement onset, trajectories showed primary evidence of an offline mode
of control (even when vision was provided) and endpoints demonstrated amplified sensitivity to the illusory (i.e., allocentric)
features of the IRE. In contrast, reaches performed with reliable visual feedback evidenced a primarily online mode of control
and showed increased visuomotor resistance to the IRE. These findings suggest that the manner a reaching response is structured
differentially influences the weighting of allocentric and egocentric visual information. More specifically, when visual feedback
is unavailable or unpredictable, the weighting of allocentric visual information for the advanced planning of a reach trajectory
is increased.
相似文献
Matthew HeathEmail: |
4.
Ghafouri M Lestienne FG 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2006,169(1):24-36
The principal goal of our study is to gain an insight into the representation of peripersonal space. Two different experiments
were conducted in this study. In the first experiment, subjects were asked to represent principal anatomical reference planes
by drawing ellipses in the sagittal, frontal and horizontal planes. The three-dimensional hand-drawing movements, which were
achieved with and without visual guidance, were considered as the expression of a cognitive process per se: the peripersonal
space representation for action. We measured errors in the spatial orientation of ellipses with regard to the requested reference
planes. For ellipses drawn without visual guidance, with eyes open and eyes closed, orientation errors were related to the
reference planes. Errors were minimal for sagittal and maximal for horizontal plane. These disparities in errors were considerably
reduced when subjects drew using a visual guide. These findings imply that different planes are centrally represented, and
are characterized, by different errors when subjects use a body-centered frame for performing the movement and suggest that
the representation of peripersonal space may be anisotropic. However, this representation can be modified when subjects use
an environment-centered reference frame to produce the movement. In the second experiment, subjects were instructed to represent,
with eyes open and eyes closed, sagittal, frontal and horizontal planes by pointing to virtual targets located in these planes.
Disparities in orientation errors measured for pointing were similar to those found for drawing, implying that the sensorimotor
representation of reference planes was not constrained by the type of motor tasks. Moreover, arm postures measured at pointing
endpoints and at comparable spatial locations in drawing are strongly correlated. These results suggest that similar patterns
of errors and arm posture correlation, for drawing and pointing, can be the consequence of using a common space representation
and reference frame. These findings are consistent with the assumption of an anisotropic action-related representation of
peripersonal space when the movement is performed in a body-centered frame. 相似文献
5.
Massimiliano Conson Elisabetta Mazzarella Carmela Donnarumma Luigi Trojano 《Neuroscience letters》2012
Motor imagery tasks (hand laterality judgment) are usually performed with respect to a self-body (egocentric) representation, but manipulations of stimulus features (hand orientation) can induce a shift to other's body (allocentric) reference frame. Visual perspective taking tasks are also performed in self-body perspective but a shift to an allocentric frame can be triggered by manipulations of context features (e.g., another person present in the to-be-judged scene). Combining hand laterality task and visual perspective taking, we demonstrated that both stimulus and context features can modulate motor imagery performance. In Experiment 1, participants judged laterality of a hand embedded in a human or non-human silhouette. Results showed that observing a human silhouette interfered with judgments on “egocentric hand stimuli” (right hand, fingers up). In Experiment 2, participants were explicitly required to judge laterality of a hand embedded in a human silhouette from their own (egocentric group) or from the silhouette's perspective (allocentric group). Consistent with previous results, the egocentric group was significantly faster than the allocentric group in judging fingers-up right hand stimuli. These findings showed that concurrent activation of egocentric and allocentric frames during mental transformation of body parts impairs participants’ performance due to a conflict between motor and visual mechanisms. 相似文献
6.
Umiltà C Priftis K Zorzi M 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,192(3):561-569
The aim of the present paper is to provide an overview of the evidence that links spatial representation with representation
of number magnitude. This aim is achieved by reviewing the literature concerning the number interval bisection task in patients
with left hemispatial neglect and in healthy participants (pseudoneglect). Phenomena like the Spatial Numerical Association
of Response Codes (SNARC) effect and the shifts of covert spatial attention caused by number processing are thought to support
the notion that number magnitude is represented along a spatially organized mental number line. However, the evidence provided
by chronometric studies is not univocal and is open to alternative, non-spatial interpretations. In contrast, neuropsychological
studies have offered convincing evidence that humans indeed represent numbers on a mental number line oriented from left to
right. Neglect patients systematically misplace the midpoint of a numerical interval they are asked to bisect (e.g., they
say that 〈5〉 is halfway between 〈2〉 and 〈6〉) and their mistakes closely resemble the typical pattern found in bisection of
true visual lines. The presence of dissociations between impaired explicit knowledge and spared implicit knowledge supports
the notion that neglect produces a deficit in accessing an intact mental number line, rather than a distortion in the representation
of that line. Other results show that the existence of a strong spatial connotation constitutes a specific property of number
representations rather than a general characteristic of all ordered sequences.
相似文献
Carlo UmiltàEmail: |
7.
To investigate whether processes controlling preparatory covert shifts of spatial attention operate within external and anatomically defined spatial coordinates, lateralized event-related potentials components sensitive to the direction of attentional shifts were measured in response to visual precues directing attention to the relevant location of tactile events. Participants had to detect infrequent tactile targets delivered to the hand located on the cued side. In different blocks, hands were uncrossed or crossed, so that external and anatomical codes specifying task-relevant locations were either congruent or incongruent. With uncrossed hands, an anterior directing attention negativity and a posterior directing attention positivity were elicited in the cue-target interval contralateral to the side of a cued attentional shift. Although the posterior effect was unaffected by hand posture, the anterior effect was delayed and reversed polarity with crossed relative to uncrossed hands. This pattern of results provides new evidence that different spatial coordinate systems may be used by separable attentional control processes. It is suggested that a posterior process operates on the basis of external spatial coordinates, whereas an anterior process is based primarily on anatomically defined spatial codes. 相似文献
8.
The present study investigated a cognitive aspect upon spatial perception, namely the impact of a true or false verbal feedback (FB) about the magnitude of body tilt on Subjective Proprioceptive Horizon (SPH) estimates. Subjects were asked to set their extended arm normal to gravity for different pitch body tilts up to 9 degrees . True FB were provided at all body tilt angles, whereas false FB were provided only at 6 degrees backward and 6 degrees forward body tilts for half of the trials. Our data confirmed previous results about the egocentric influence of body tilt itself upon SPH: estimates were linearly lowered with forward tilts and elevated with backward tilts. In addition, results showed a significant effect of the nature of the external FB provided to the subjects. When subjects received a false FB inducing a 3 degrees forward bias relative to physical body tilt, they set their SPH consequently higher than when they received a false FB inducing a 3 degrees backward bias. These findings clearly indicated that false cognitive information about body tilt might significantly modify the judgement of a geocentric direction of space, such as the SPH. This may have deleterious repercussions in aeronautics when pilots have to localize external objects relative to earth-based directions in darkened environments. 相似文献
9.
D. Boussaoud Frank Bremmer 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1999,128(1-2):170-180
Visual information is mapped with respect to the retina within the early stages of the visual cortex. On the other hand, the
brain has to achieve a representation of object location in a coordinate system that matches the reference frame used by the
motor cortex to code reaching movement in space. The mechanism of the necessary coordinate transformation between the different
frames of reference from the visual to the motor system as well as its localization within the cerebral cortex is still unclear.
Coordinate transformation is traditionally described as a series of elementary computations along the visuomotor cortical
pathways, and the motor system is thought to receive target information in a body-centered reference frame. However, neurons
along these pathways have a number of similar properties and receive common input signals, suggesting that a non-retinocentric
representation of object location in space might be available for sensory and motor purposes throughout the visuomotor pathway.
This paper reviews recent findings showing that elementary input signals, such as retinal and eye position signals, reach
the dorsal premotor cortex. We will also compare eye position effects in the premotor cortex with those described in the posterior
parietal cortex. Our main thesis is that appropriate sensory input signals are distributed across the visuomotor continuum,
and could potentially allow, in parallel, the emergence of multiple and task-dependent reference frames.
Received: 21 September 1998 / Accepted: 19 March 1999 相似文献
10.
A great effort has been made to identify crucial cognitive markers that can be used to characterize the cognitive profile of Alzheimer's disease (AD). Because topographical disorientation is one of the earliest clinical manifestation of AD, an increasing number of studies have investigated the spatial deficits in this clinical population. In this systematic review, we specifically focused on experimental studies investigating allocentric and egocentric deficits to understand which spatial cognitive processes are differentially impaired in the different stages of the disease. First, our results highlighted that spatial deficits appear in the earliest stages of the disease. Second, a need for a more ecological assessment of spatial functions will be presented. Third, our analysis suggested that a prevalence of allocentric impairment exists. Specifically, two selected studies underlined that a more specific impairment is found in the translation between the egocentric and allocentric representations. In this perspective, the implications for future research and neurorehabilitative interventions will be discussed. 相似文献
11.
Stella F. Lourenco Matthew R. Longo 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,193(1):151-156
Although the spatial representation of number (mental number line) is well documented, the scaling associated with this representation is less clear. Sometimes people appear to rely on compressive
scaling, and sometimes on linear scaling. Here we provide evidence for both compressive and linear representations on the
same numerical bisection task, in which adult participants estimate (without calculating) the midpoint between two numbers.
The same leftward bias (pseudoneglect) shown on physical line bisection appears on this task, and was previously shown to increase with the magnitude of bisected
numbers, consistent with compressive scaling (Longo and Lourenco in Neuropsychologia 45:1400–1407, 2007). In the present study, participants held either small (1–9) or large (101–109) number primes in memory during bisection.
When participants remembered small primes, bisection responses were consistent with compressive scaling. However, when they
remembered large primes, responses were more consistent with linear scaling. These results show that compressive and linear
representations may be accessed flexibly on the same task, depending on the numerical context. 相似文献
12.
Paul Dassonville 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1995,106(3):434-448
As the hand actively explores the environment, contact with an object leads to neuronal activity in the topographic maps of somatosensory cortex. However, the brain must combine this somatotopically encoded tactile information with an internal representation of the hand's location in space if it is to determine the position of the object in three-dimensional space (3-D haptic localization). To investigate the fidelity of this internal representation in human subjects, a small tactual stimulator, light enough to be worn on the subject's hand, was used to present a brief mechanical pulse (6-ms duration) to the right index finger before, during, or after a fast, visually evoked movement of the right hand. In experiment 1, subjects responded by pointing to the perceived location of the mechanical stimulus in 3-D space. Stimuli presented shortly before or during the visually evoked movement were systematically mislocalized, with the reported location of the stimulus approximately equal to the location occupied by the hand 90 ms after stimulus onset. This pattern of errors indicates a representation of the movement that fails to account for the change in the hand's location during somatosensory delays and, in some subjects, inaccurately depicts the velocity of the actual movement. In experiment 2, subjects were instructed to verbally indicate the perceived temporal relationship of the stimulus and the visually evoked movement (i.e., by reporting whether the stimulus was presented before, during, or after the movement). On average, stimuli presented in the 38-ms period before movement onset were more likely to be perceived as having occurred during rather than before the movement. Similarly, stimuli in the 145-ms period before movement termination were more likely to be perceived as having occurred after rather than during the movement. The analogous findings of experiments 1 and 2 indicate that the same inaccurate representation of dynamic hand position is used to both localize tactual stimuli in 3-D space and construct the perception of arm movement. 相似文献
13.
The most common behavioral test of hippocampus-dependent, spatial learning and memory is the Morris water task, and the most commonly studied behavioral correlate of hippocampal neurons is the spatial specificity of place cells. Despite decades of intensive research, it is not completely understood how animals solve the water task and how place cells generate their spatially specific firing fields. Based on early work, it has become the accepted wisdom in the general neuroscience community that distal spatial cues are the primary sources of information used by animals to solve the water task (and similar spatial tasks) and by place cells to generate their spatial specificity. More recent research, along with earlier studies that were overshadowed by the emphasis on distal cues, put this common view into question by demonstrating primary influences of local cues and local boundaries on spatial behavior and place-cell firing. This paper first reviews the historical underpinnings of the "standard" view from a behavioral perspective, and then reviews newer results demonstrating that an animal's behavior in such spatial tasks is more strongly controlled by a local-apparatus frame of reference than by distal landmarks. The paper then reviews similar findings from the literature on the neurophysiological correlates of place cells and other spatially correlated cells from related brain areas. A model is proposed by which distal cues primarily set the orientation of the animal's internal spatial coordinate system, via the head direction cell system, whereas local cues and apparatus boundaries primarily set the translation and scale of that coordinate system. 相似文献
14.
The study tested whether nociceptive stimuli applied to a body limb can orient spatial attention in external space toward visual stimuli delivered close to that limb. Nociceptive stimuli were applied to either the left or the right hand. Task‐relevant visual stimuli were delivered at the location adjacent to the stimulated hand (70% valid trials) or adjacent to the other hand (30% invalid trials). Visual stimuli were discriminated with shorter reaction times and elicited ERPs of greater magnitude in the valid as compared to the invalid trials. This enhancement affected the N1 component, suggesting that the location of the nociceptive cue modifies visual processing through a modulation of neural activity in the visual cortex. We hypothesize the existence of a common frame of reference able to coordinate the mapping of the space of the body and the mapping of the external space. 相似文献
15.
Introduction. There has been a relative lack of research on deaf people with schizophrenia, and no data exist regarding symptom structure in this population. Thus, we determined the factor structure of the 24-item Brief Psychiatric Rating Scale (BPRS) in deaf (n=34) and hearing (n=31) people with schizophrenia and compared it to a standard four-factor solution. Method. An obliquely rotated factor analysis produced a solution for the BPRS that resembled others in the literature. Symptom clusters were additionally compared to cognitive and social-cognitive abilities. Results. Activity and disorganised symptoms were the most consistent correlates of visual- and thought and language-related skills for deaf and hearing subjects respectively. Affective symptoms and facial affect processing were positively correlated among deaf but not hearing subjects. Conclusions. The data suggest that current symptom models of schizophrenia are valid in both hearing and deaf patients. However, relations between symptoms, cognition, and outcome from the general (hearing) literature cannot be generalised to deaf patients. Findings are broadly consistent with pathophysiologic models of schizophrenia suggesting a fundamental cortical processing algorithm operating across several domains of neural activity including vision, and thought and language. Support is provided for recent advances in social-cognitive interventions for people with schizophrenia. 相似文献
16.
Interactions of different body parts in peripersonal space: how vision of the foot influences tactile perception at the hand 总被引:1,自引:0,他引:1
Schicke T Bauer F Röder B 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,192(4):703-715
The body schema, a constantly updated representation of the body and its parts, has been suggested to emerge from body part-specific
representations which integrate tactile, visual, and proprioceptive information about the identity and posture of the body.
Studies using different approaches have provided evidence for a distinct representation of the visual space ~30 cm around
the upper body, and predominantly the hands, termed the peripersonal space. In humans, peripersonal space representations
have often been investigated with a visual–tactile crossmodal congruency task. We used this task to test if a representation
of peripersonal space exists also around the feet, and to explore possible interactions of peripersonal space representations
of different body parts. In Experiment 1, tactile stimuli to the hands and feet were judged according to their elevation while
visual distractors presented near the same limbs had to be ignored. Crossmodal congruency effects did not differ between the
two types of limbs, suggesting a representation of peripersonal space also around the feet. In Experiment 2, tactile stimuli
were presented to the hands, and visual distractors were flashed either near the participant’s foot, near a fake foot, or
in distant space. Crossmodal congruency effects were larger in the real foot condition than in the two other conditions, indicating
interactions between the peripersonal space representations of foot and hand. Furthermore, results of all three conditions
showed that vision of the stimulated body part, compared to only proprioceptive input about its location, strongly influences
crossmodal interactions for tactile perception, affirming the central role of vision in the construction of the body schema.
相似文献
Tobias SchickeEmail: |
17.
Terry AV Gearhart DA Warner S Hohnadel EJ Middlemore ML Zhang G Bartlett MG Mahadik SP 《Neuroscience》2007,150(2):413-424
The primary therapeutic agents used for schizophrenia, antipsychotic drugs, ameliorate psychotic symptoms; however, their chronic effects on cognition (or the physiologic processes of the brain that support cognition) are largely unknown. The purpose of this rodent study was to extend our previous work on this subject by investigating persistent effects (i.e. during a 14 day drug-free washout period) of chronic treatment (i.e. ranging from 45 days to 6 months) with a representative first and second generation antipsychotic. Drug effects on learning and memory and important neurobiological substrates of memory, the neurotrophin, nerve growth factor (NGF) and its receptors, and certain components of the basal forebrain cholinergic system were investigated. Behavioral effects of oral haloperidol (2.0 mg/kg/day), or risperidone (2.5 mg/kg/day) were assessed in an open field, a water maze task, and a radial arm maze procedure and neurochemical effects in brain tissue were subsequently measured by enzyme-linked immunosorbent assays (ELISAs). The results indicated that both antipsychotics produced time-dependent and protracted deficits in the performance of a water maze procedure when compared with vehicle-treated controls, while neither drug was associated with significant alterations in radial arm maze performance. Interestingly, haloperidol, but not risperidone, was detectible in the rodent brain in appreciable levels for up to 2 weeks after drug discontinuation. Both antipsychotics were also associated with reduced levels of NGF protein in the basal forebrain and prefrontal cortex and significant (or nearly significant) decreases in phosphorylated tropomyosin-receptor kinase A (TrkA) protein and the vesicular acetylcholine transporter (depending on the brain region analyzed). Neither antipsychotic markedly affected TrkA or p75 neurotrophin receptor levels. These data in rats indicate that chronic treatment with either haloperidol or risperidone may be associated with protracted negative effects on cognitive function as well as important neurotrophin and neurotransmitter pathways that support cognition. 相似文献
18.
19.
Silvio Ionta Olaf Blanke 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,195(2):207-217
The representation of the body in the brain is continuously updated with regard to peripheral factors such as position or
movement of body parts. In the present study, we investigated the effects of arm posture on the mental rotation of hands and
feet. Sixteen right-handed and ten left-handed participants verbally judged the laterality of visually presented pictures
of hands and feet in two different postural conditions. In one condition they placed their right hand on their right knee
and their left hand behind the back, in the other condition the hand position was reversed. For right-handed participants
response times for the laterality judgment of right hands increased when participants kept their right hand behind the back.
This was not found for images of the left hand nor for images of the feet. For the left-handed participants, there was no
effect of arm posture on hand or feet stimulus judgments. Thus, the body-part posture effect on mental rotation was found
to be specific for the side and the body part for which the posture was modified only in right-handed participants, but it
was absent for left-handed participants. For both samples, we also found a progressive disruption of the mental rotation function
depending on the view from which the body parts were seen (i.e. dorsal, thumb/big toe, palm/plantar, little finger/toe). Posture
and view effects on body parts representations are discussed with respect to proprioception, handedness, visual familiarity
and the influence of anatomical joint constraints on motor imagery. 相似文献
20.
We have investigated effects of letrozole, an aromatase inhibitor, on spatial learning and memory, expression of neural cell adhesion molecules (NCAM) and catecholaminergic neurotransmitters in the hippocampus and cortex of female rats. In the intact model, adult Sprague-Dawley rats were divided into four groups (n=8). Control received saline alone. Letrozole was administered to the animals in the second and third groups by daily oral gavage at 0.2 and 1 mg/kg doses, respectively, for 6 weeks. Another group of letrozole-treated rats was allowed to recover for 2 weeks. In the second model, 24 rats were ovariectomized (ovx) and the first group served as control. The second group received letrozole (1 mg/kg) for 6 weeks. Ovx rats in the third group were given letrozole (1 microg/kg) plus estradiol (E(2)) (10 microg/rat). At the end, all rats were tested in a spatial version of the Morris water maze. Then they were decapitated and the brains rapidly removed. Catecholamine concentrations were determined by high performance liquid chromatography with electrochemical detection. NCAM 180, 140 and 120 isoforms were detected by Western blotting. Uterine weights were significantly reduced by letrozole in a dose-dependent manner (P<0.01) which returned to control values following 2 weeks of recovery (P<0.05). Serum E(2) levels followed a similar course (P<0.01). Although improvement in spatial learning performance of letrozole-treated rats was not statistically significant, the high-dose letrozole-treated group remained significantly longer in the target quadrant compared with the control (P<0.05). Administration of letrozole to ovx animals significantly reduced the latency (P<0.001) and increased the probe trial performance compared with ovx controls (P<0.05). Letrozole increased expression of NCAM 180 and NCAM 140 in both hippocampus and cortex of intact rats. In the cortex samples of ovx animals, NCAM 180 was overall lower than the intact control values (P<0.05). Noradrenaline, dopamine and their metabolites were decreased in the hippocampus of the letrozole-treated group (P<0.01). Letrozole had differential effects on noradrenaline and dopamine content in the cortex. It appears that inhibition of estrogen synthesis in the brain may have beneficial effects on spatial memory. We suggest that structural changes such as NCAM expression and catecholaminergic neurotransmitters in the hippocampus and prefrontal cortex may be the neural basis for estrogen-dependent alterations in cognitive functions. 相似文献