Photoparoxysmal response elicited by flickering dot pattern stimulation to the center and periphery.

OBJECTIVE: We performed this study to elucidate the roles of stimulus spatial frequency and visual field in eliciting generalized photoparoxysmal response (PPR) by flickering dot pattern (FDP) stimulation. METHODS: We studied 20 photosensitive epilepsy patients, aged 7-48 years (means +/- SD, 21.4+/-11.7 years), producing a 20 Hz FDP stimulation with a strobo-filter. Using dot patterns (0.5, 1, 2, 4 and 6 mm in diameter), we gave FDP stimulation to the center (11x11 degrees ) and periphery (11-30x11-30 degrees ) of subjects with eyes open, and analyzed each PPR appearance latency. RESULTS: Significant results were: latency by 1 (2.1 c/deg) and 0.5 mm (4.9 c/deg) FDP stimulation to the center was shorter than that to the periphery; latency by 4 mm (0.8 c/deg) FDP stimulation to the periphery was shorter than that to the center. As for 2 (1.5 c/deg) and 6 mm (0.5 c/deg) FDP stimuli, no significant difference could be observed. CONCLUSIONS: A higher spatial frequency FDP stimulation to the center elicits PPR more strongly than that to the periphery, whereas a lower spatial frequency FDP stimulation showed the opposite result, with peripheral stimulation being more effective than central stimulation.     

Vector analysis of visual evoked potentials elicited by pattern reversal and photic stimuli.

OBJECTIVE: The 2D VEPs to pattern reversal (PR) and LED goggle were studied in order to obtain a stable parameter for the functional assessing of posterior visual pathways regardless of the stimulus type used. DESIGN AND METHODS: Apex c latency, bc segment amplitude (V), and bc vector orientation angle (theta) in voltage space were computed from VEPs recorded in 50 normal human beings and two patients with left posterior brain lesions, in an orthogonal Fpz-Oz and T3-T4 montage and displayed as a two channel Lissajous' trajectory. The effects of stimulus type and stimulated eye were analyzed in the normal group by a two-way ANOVA. RESULTS: The stimulated eye had no effect on any parameter. Apex c latency was slightly longer, and V was greater and more variable in the responses to goggle stimuli, but there was no significant difference in theta, oriented to mid-occipital scalp with very low variability for both stimulus types. The patients showed significant deviations of theta towards the affected hemisphere. CONCLUSIONS: The bc vector orientation (theta) is a stable parameter for the evaluation of the posterior visual pathways using both pattern reversal and LED stimuli, specially the latter, useful in unconscious or uncooperative patients.     

Photic driving evoked by hemifield flickering dot pattern stimulation in a patient with brain tumor

We have described photic driving evoked by hemifield 5/sec flickering dot pattern stimulation in a patient suffering from a metastatic tumor in the left parietal lobe. Based on an analysis of the photic driving in this particular patient, the left upper lip of the visual cortex is presumed to be the most sensitive to 5/sec flickering dot pattern stimulation. It is suggested that such an examination might be useful for determining local functional disturbance in the visual cortex.     

Somatosensory evoked potentials (SEPs) and cortical single unit responses elicited by mechanical tactile stimuli in awake monkeys

The origins of surface recorded evoked potentials have been investigated by combining recordings of single unit responses and somatosensory evoked potentials (SEPs) from the postcentral gyrus of 4 alert macaque monkeys. Responses were elicited by mechanical tactile stimuli (airpuffs) which selectively activate rapidly adapting cutaneous mechanoreceptors, and permit patterned stimulation of a restricted area of skin. Epidurally recorded SEPs consisted of an early positive complex, beginning 8-10 msec after airpuff onset, with two prominent positive peaks (P15 and P25), succeeded by a large negative potential (N43) lasting 30 msec, and a late slow positivity (P70). SEPs, while consistent in wave form, varied slightly between monkeys. The amplitude of the early positive complex was enhanced by increasing the number of stimulated points, or by placing the airpuffs in the receptive fields of cortical neurons located beneath the SEP recording electrode. SEP amplitude was depressed when preceded 20-40 msec earlier by a conditioning stimulus to the same skin area. Single unit responses in areas 3b and 1 of primary somatosensory (SI) cortex consisted of a burst of impulses, beginning 11-12 msec after the airpuff onset, and lasting another 15-20 msec. Peak unitary activity occurred at 12-15 msec, corresponding to the P15 wave in the SEP. No peak in SI unit responses occurred in conjunction with the P25 wave. Although SI neurons fired at lower rates during P25, the lack of any peak in SI unit responses suggests that activity in other cortical areas, such as SII cortex, contributes to this wave. Most unit activity in SI cortex ceased by the onset of N43, and was replaced by a period of profound response depression, in which unit responses to additional tactile stimuli were reduced. We propose that the N43 wave reflects IPSPs in cortical neurons previously depolarized and excited by the airpuff stimulus. Late positive potentials (P70) in the SEP had no apparent counterpart in SI unit activity, suggesting generation at other cortical loci.     

The role of disgust in faintness elicited by blood and injection stimuli

To examine the role of disgust in blood-injection fear and faintness, 79 individuals high and low in disgust and distressed either more by blood or injections were exposed to both a blood slide and a needle slide. Self-reported faintness and systolic and diastolic blood pressure were measured. High disgust individuals reported more faintness to both slides, but those who were more distressed by blood reported more faintness to the blood slide and those who were more distressed by needles reported more fear to the needle slide. Both systolic and diastolic blood pressure assessments manifested a diphasic response. The diphasic response pattern was most evident among the high disgust subjects, who were more distressed by blood than injections. Results are discussed in terms of the relevance of disgust in the etiology of fear and faintness in blood-injury phobia.     

Differential effects of constant light on circadian clock resetting by photic and nonphotic stimuli in Syrian hamsters

Circadian rhythms in Syrian hamsters can be phase shifted by behavioral arousal during the usual rest phase of the circadian rest-activity cycle. Phase shifts can be greatly potentiated by exposing the animals to constant light for 1 or 2 cycles. This could reflect a change in a specific nonphotic input pathway to the suprachiasmatic nucleus (SCN) circadian pacemaker, or it could be caused by a change in the amplitude of the pacemaker. If the latter, then phase shifts to any stimulus, including those activating the photic input pathway, should be potentiated. This hypothesis was tested by measuring phase shifts induced by microinjections of NMDA (500 nl, 10 mM) into the SCN area of hamsters exposed to constant light or dark for 2 days. NMDA induced significant phase delay shifts that mimicked those induced by light exposure early in the night. The magnitude of these shifts did not differ by prior lighting condition. Shifts induced by NMDA (200 nl, 10 mM) microinjections on day 3 and 13 of LL also did not differ. Phase shifts induced by a nonphotic stimulus (3 h of running stimulated by confinement to a novel wheel) were significantly potentiated by 2 days of exposure to constant light. These results indicate that exposure to constant light for 2 circadian cycles differentially affects phase resetting responses to photic and nonphotic inputs to the circadian pacemaker, suggesting that potentiation of shifts to nonphotic stimuli reflect changes in a nonphotic input pathway rather than in an amplitude dimension of the circadian pacemaker.     

Behavioral and physiological studies of non-narcotic analgesia in the rat elicited by certain environmental stimuli

These experiments characterized the analgesia resulting from exposure to certain noxious and/or stressful manipulations. Rats exposed either to electric grid shock (0.35-2.0 mA for 10-30 sec) or to 5 min of presumably non-painful centrifugal rotation (about 7.0 transverse g's) were analgesic as measured by tail-flick, hot plate and responses to applications of a calibrated paw pinch or alligator clip. Analgesia produced by shock (SA) or centrifugal rotation (RA) persisted after termination of these manipulations. Neither SA nor RA were attended by generalized sensory, attentional or motoric deficits. Intraperitoneal injection of hypertonic saline also increased tail-flick latencies. Exposure to brief ether anesthesia or horizontal oscillation, both of which have been reported to increase ACTH secretion (a commonly used indicator of stress), did not produce analgesia as measured by the tail-flick test. The use of classical conditioning procedures to pair shock with environmental stimuli resulted in increased tail-flick latencies. The narcotic antagonist naloxone (1 mg/kg, i.p.) did not reduce the tail-flick inhibition produced by shock, rotation, hypertonic saline or classical conditioning. Chlordiazepoxide (5 mg/kg, i.p.) also failed to antagonize the increased tail-flick latencies produced by shock or conditioning. Tail-flick inhibition produced by shock or rotation was markedly reduced by complete spinal cord transection at thoracic levels. These results suggest that: (1) the selective modulation of nociceptive input at the level of the spinal cord can be mediated by a supraspinal system or systems physiologically distinct from those involved in analgesia produced by the administration of opiates; (2) non-narcotic modulation of nociceptive input occurring within the spinal cord can be learned by exposure to classical conditioning procedures; and (3) noxious stimuli are sufficient but not necessary to produce a non-narcotic analgesia; stress alone, however, is not always sufficient to produce this analgesia.     

Electrical stimulation of the dorsal hippocampus caused a long lasting inhibition of ACTH and adrenocortical responses to photic stimuli in freely moving rats

The effect of a single train of electrical hippocampal stimulation on ACTH and corticosterone (CS) responses to subsequent photic stimulation was studied in freely moving male rats. The hippocampal stimulation inhibited the stress-induced rise [corrected] in serum CS levels up to 150 h when compared to sham stimulated animals. This effect did not exist at 300 h following stimulation. This sustained hippocampal inhibitory effect on the adrenocortical response, which was not reported previously, was partially abolished by section of the dorsal fornix. The present data demonstrate that dorsal hippocampal stimulation has a long lasting inhibitory effect on pituitary adrenocortical secretion following neural stimuli and this is partially mediated by the dorsal fornix.     

精神分裂症患者脑额--顶皮质联络障碍的脑电图相干性分析

目的　用脑电图 (EEG)额—顶位点相干性分析方法 ,验证精神分裂症患者存在额—顶皮质联络障碍的假说。方法　采用病例 对照研究设计。患者组包括发病后未经治疗 (2 5例 )或停止治疗 (15例 ) 3周以上的精神分裂症患者 ,对照组为 4 1名健康正常人。相干性指标包括安静状态和 1Hz闪光刺激状态EEGα峰频率左、右额—顶 (F3/P3,F4 /P4 )和额叶 (F3/F4 )、顶叶 (P3/P4 )位点半球间相干系数。用多变量方差分析比较组间差别。结果　安静EEG相干性 ,患者组与正常对照组的差别无显著性。闪光刺激EEG相干性 ,未治疗和停药患者左、右半球额—顶低于正常对照组 (左 :0 6 5±0 2 0vs 0 73± 0 15vs 0 77± 0 10 ,F2 ,75=4 5 8,P =0 0 1;右 :0 6 7± 0 19vs 0 72± 0 15vs 0 77±0 15 ,F2 ,75=3 6 2 ,P =0 0 3) ,额叶、顶叶位点半球间相干性与正常对照组的差别则无显著性 (F检验 ,P >0 0 5 )。患者组EEG相干性 ,偏执型患者与其他型患者的差别无显著性 (P >0 0 5 ) ,与年龄、教育年限、发病年龄、总病程和病情严重程度的相关无显著性。结论　精神分裂症患者存在额—顶皮质联络障碍 ,并可能是神经发育性的。     

阿立哌唑对抗精神病药物所致的老年精神分裂症患者高催乳素血症的影响

目的:探讨阿立哌唑对抗精神病药物所致的老年精神分裂症患者高催乳素血症的影响.方法:63例抗精神病药所致高催乳素血症的老年精神分裂症患者随机分为研究组(33例)和对照组(30例).两组沿用原有抗精神病药物,研究组加用阿立哌唑5 mg/d持续12周.分别于入组前、入组4、8、12周末检测血清催乳素水平,同时采用简明精神病评定量表(BPRS)和治疗中出现的症状量表(TESS)评定精神病性症状及药物不良反应. 结果:入组4、8、12周末研究组血清催乳素水平较入组前及对照组显著降低(P均＜0.05);对照组入组前后血清催乳素水平差异无统计学意义(P均＞0.05).两组人组前后BPRS、TESS评分差异无统计学意义(P均＞0.05). 结论:阿立哌唑可有效降低抗精神病药物所致老年精神分裂症患者血清催乳素水平增高,且并未增加药物不良反应.     

Development of visual evoked potentials and photic driving responses in normal full term, low risk premature, and Trisomy-21 infants during the first year of life

Stroboscopic visual evoked potentials (SVEPs) and photic driving responses were recorded during the first week of life post term and at 4, 13, 26 and 52 weeks in normal full term, low risk premature, and Trisomy-21 infants. The age effect on SVEP P2 peak latency was significant (P less than 0.001). P2 latency for the Trisomy-21 group was significantly prolonged at 1 week of age only. Voltages and interhemispheric symmetry were highly variable, with no significant age or group effects. There is considerable variability in photic driving effects, even within sessions. Maximal driving frequencies are difficult to determine; they may be near 15 Hz at term. The age effect on optimal driving frequency (3-4 Hz at week 1 increasing to 5 Hz at 12 months) was significant (P less than 0.001). The between-groups effect was not significant. The results are discussed in terms of (1) our own previous results, (2) previous results reported in the literature, and (3) significance in clinical applications.     

Effects of changes in heart rate in different body positions upon critical flicker fusion threshold and reaction time performance in patients with artificial pacemakers

Critical flicker fusion threshold and two-choice reaction time performances were measured in eight patients, aged 49–79 yr, treated with artificial pacemakers for complete heart block (six cases) or atrial bradycardia (two cases), at heart rates of 71 and 44 beats/min in both sitting and supine position. In sitting position, critical flicker fusion threshold was significantly decreased and reaction time performances were significantly prolonged at the lower heart rate. In supine position, there was no such decrease in critical flicker fusion threshold, but reaction time performances were still significantly longer at the lower rate. These findings may be explained in terms of differences in circulatory dynamics between the two heart rates and body positions and to a consequent cerebral hypoxia at the lower heart rate, most pronounced in the sitting position.     

Opioid modulation and sensitization of dopamine release elicited by sexually relevant stimuli: a high speed chronoamperometric study in freely behaving rats

High speed chronoamperometry was used to measure oxidation and reduction currents associated with monoamine release in the caudate putamen and nucleus accumbens of freely moving rats exposed to bedding from cages that housed other male, ovariectomized female, or estradiol-progesterone-primed female rats. Estrus female, but not male or ovariectomized female bedding potently increased the electrochemical signal from electrodes implanted within the nucleus accumbens, and less effectively from more dorsal sites. Naloxone pretreatment attenuated the increase in the electrochemical signal. Repeated exposure to estrus female bedding led to an increased, or sensitized, response within the nucleus accumbens that was also sensitive to naloxone pretreatment. The ratios of the reduction to oxidation currents indicated that dopamine was the principal contributor to the increase in the electrochemical signal, suggesting that activation of the mesolimbic dopamine system accompanies exposure to sexually relevant stimuli. These results suggest that the facilitation of sexual behaviors by dopamine may be due, at least in part, to the processing of incentive motivational cues, and not necessarily to effects on copulation, itself. The results of the present study also suggest that opioid peptides contribute to the activation of mesolimbic dopamine by sexually relevant olfactory stimuli.     

盐酸多奈哌齐治疗老年轻度认知功能障碍的临床疗效及脑电功能评价

目的 探讨盐酸多奈哌齐治疗老年轻度认知功能障碍(MCI)患者的临床疗效及脑电图(EEG)、事件相关电位(ERP)P300的变化. 方法 选取上海交通大学附属上海市第六人民医院老年科自2009年1月至2010年3月就诊的115例老年MCI患者,按完全随机数字表法分为盐酸多奈哌齐联合银杏叶制剂治疗组(治疗组,58例)和单用银杏叶制剂治疗组(对照组,57例),观察2组患者治疗前后简易精神状况检查量表(MMSE)评分以及EEG、P300的改变,评估临床疗效,并在组间进行比较. 结果 治疗后2组患者MMSE评分均较治疗前有所提高,但治疗组提高更为明显,与治疗前和对照组比较差异均有统计学意义(P＜0.05).治疗组的EEG异常率(25.86％)明显低于对照组(45.61％),差异有统计学意义(P＜0.05).治疗后2组患者P300潜伏期均有缩短、波幅增高,但治疗组变化更为明显,与治疗前及对照组比较差异均有统计学意义(P＜0.05).秩和检验发现治疗组临床疗效明显优于对照组,差异有统计学意义(P＜0.05). 结论 与单用银杏叶制剂比较,盐酸多奈哌齐联合银杏叶制剂治疗能显著改善老年MCI患者认知功能及脑电活动状态,提示盐酸多奈哌齐在老年MCI治疗中有一定价值.