How is electrical stimulation of the brain experienced,and how can we tell? Selected considerations on sensorimotor function and speech

ABSTRACT

Electrical stimulation of the nervous system is a powerful tool for localizing and examining the function of numerous brain regions. Delivered to certain regions of the cerebral cortex, electrical stimulation can evoke a variety of first-order effects, including observable movements or an urge to move, or somatosensory, visual, or auditory percepts. In still other regions the subject may be oblivious to the stimulation. Often overlooked, however, is whether the subject is aware of the stimulation, and if so, how the stimulation is experienced by the subject. In this review of how electrical stimulation has been used to study selected aspects of sensorimotor and language function, we raise questions that future studies might address concerning the subjects’ second-order experiences of intention and agency regarding evoked movements, of the naturalness of evoked sensory percepts, and of other qualia that might be evoked in the absence of an overt first-order experience.     

Factors contributing to blood pressure elevation during norepinephrine and phenylephrine infusions in dogs

To examine the factors contributing to the rise in systemic blood pressure during α- and β- adrenergic stimulation, phenylephrine, an α-adrenergic agonist, and norepinephrine, an α- and β-adrenergic agonist, were infused intravenously to anesthetized dogs until mean aortic blood pressure was raised equally by 40–60 mmHg. Changes in preload were estimated by changes in left ventricular end-diastolic pressure or segment length recorded by an ultrasonic technique. By obstructing the inferior vena cava (IVC), the increase in preload could be reduced to control level during phenylephrine and norepinephrine infusions without altering peripheral resistance (mean aortic blood pressure/cardiac output). Normalization of preload reduced the pressure response by 2/3 during phenylephrine infusion and by 1/4 during norepinephrine infusion. However, after β-adrenergic blockade by propranolol, normalization of preload reduced the pressure response by 2/3 during both phenylephrine and norepinephrine infusions. Thus, during α-adrenergic stimulation, the increase in preload is a more important factor than the increase in peripheral resistance. Norepinephrine raised stroke volume by 24±5%. When the increase in stroke volume was prevented by IVC obstruction, the pressure response to norepinephrine was halved. Thus, during norepinephrine infusion the rise in stroke volume caused by β-adrenergic stimulation is as important as α-adrenergic stimulation for the pressure response.     

Action of burn serum on electrical and contractile activity of the homoiothermic myocardium

In experiments on isolated rabbit papillary muscles the action of burn serum (BS) obtained 1 h after thermal injury to rabbits was studied. During stimulation varying in frequency between 0.1 and 2 Hz isometric contractions and action potentials (AP) of myocardial cells were recorded. BS (diluted 1:1 in Tyrode solution) inhibited the contractile activity of the papillary muscles, increased the duration of AP, and reduced the duration of the contractile response. Inotropic effects on the rhythm of contractions remained unchanged: An increase in the frequency of stimulation to 2 Hz led to an increase in the amplitude of contractions. Inhibition of the contractile response increased progressively with an increase in the duration of perfusion of the preparations with BS. Addition of 6.4 mM Ca⁺⁺ to the solution of BS caused only a temporary increase in contractions, and rinsing the preparations with Tyrode solution did not result in complete recovery of the orginal contractions. It is concluded that humoral factors play an important role in the disturbance of the contractile properties of heart muscle during burn shock.Laboratory of Biophysical Research, A. V. Vishnevskii Institute of Surgery, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR M. I. Kuzin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 8, pp. 157–159, August, 1979.     

Physiological Detection of Deception: Measurement of Responses to Questions and Answers During Countermeasure Maneuvers

Physiological detection of deception (“lie detection”) procedures were evaluated with 24 actors, half of whom were “guilty” of a mock-crime and half were “innocent.” All subjects were trained in the Stanislavsky method of acting and were instructed to use this method to appear innocent on the polygraph test. Two versions of the control question detection of deception test were employed: one in which subjects verbally answered immediately following each question and the other in which they delayed their verbal answer for 8 sec following each question. The delayed answer technique allowed the separate measurement of physiological responses to the questions and the answers. Skin resistance responses, cardiovascular changes, and respiration were recorded and analyzed. Excluding inconclusive results, the overall accuracy of the decisions varied between 78% and 91% depending on the test employed. The principal results were: 1) attempts by guilty subjects to appear innocent were totally ineffective, 2) physiological responses elicited by the questions were more valid indicators of deception and nondeception than were the responses elicited by the verbal answers, and 3) errors occurred more frequently with innocent subjects (between 17% and 25% depending on the measure used) than with guilty subjects (0% with each measure). Variables which may affect the generalizability of these results to the field situation are discussed and suggestions for increasing the generalizability of laboratory findings are made.     

Blood flow velocity in the common carotid artery in humans during graded exercise on a treadmill

Cerebral blood volume flow and flow velocity have been reported to increase during dynamic exercise, but whether the two increase in parallel and whether both increases occur as functions of exercise intensity remain unsettled. In this study, blood flow velocity in the common carotid artery was measured using the Doppler ultrasound method in eight healthy male students during graded treadmill exercise. The exercise consisted of stepwise progressive increases and decreases in exercise intensity. The peak intensity corresponded to approximately 85% of maximal oxygen consumption. During this exercise, the heart rate (f _c), mean blood pressure (BP) in the brachial artery and mean blood flow velocity (_cc) in the common carotid artery increased as functions of exercise intensity. At the peak exercise intensity, (f _c), BP and _cc increased by 134.5%, 20.5% and 51.8% over the control levels before exercise (P < 0.01), respectively. The resistance index (RI) and pulsatility index (PI) were determined from the velocity profile and were expected to reflect the distal cerebral blood flow resistance. The RI and PI increased during the graded exercise, but tended to decrease at the highest levels of exercise intensity. As _cc increased with increases in exercise intensity it would be expected that cerebral blood flow would also increase at these higher intensities. It is also suggested that blood flow velocity in the cerebral artery does not proportionately reflect the cerebral blood flow during dynamic exercise, since the cerebral blood flow resistance changes.     

细菌对噬菌体感染的抵抗

噬菌体对其宿主菌具有特异性感染力,反之,宿主菌对噬菌体的感染具有抵抗现象.根据噬菌体侵入宿主的不同阶段,可以将宿主菌对噬菌体的天然抵抗机制分为4个主要的类别吸附抑制,流产感染,限制-修饰系统和穿入阻滞.此外,还有源于噬菌体的抗性作用以及通过人工插入突变获得的广谱噬菌体抗性菌株等.     

Dipolar sources of the early scalp somatosensory evoked potentials to upper limb stimulation Effect of increasing stimulus rates

Brain electrical source analysis (BESA) of the scalp electroencephalographic activity is well adapted to distinguish neighbouring cerebral generators precisely. Therefore, we performed dipolar source modelling in scalp medium nerve somatosensory evoked potentials (SEPs) recorded at 1.5-Hz stimulation rate, where all the early components should be identifiable. We built a four-dipole model, which was issued from the grand average, and applied it also to recordings from single individuals. Our model included a dipole at the base of the skull and three other perirolandic dipoles. The first of the latter dipoles was tangentially oriented and was active at the same latencies as the N20/P20 potential and, with opposite polarity, the P24/N24 response. The second perirolandic dipole showed an initial peak of activity slightly earlier than that of the N20/P20 dipolar source and, later, it was active at the same latency as the central P22 potential. Lastly, the third perirolandic dipole exaplaining the fronto-central N30 potential scalp distribution was constantly more posterior than the first one. In order to evaluate the effect of an increasing repetition frequency on the activity of SEP dipolar sources, we applied the model built from 1.5-Hz SEPs to traces recorded at 3-Hz and 10-Hz repetition rates. We found that the 10-Hz stimulus frequency reduced selectively the later of the two activity phases of the first perirolandic dipole. The decrement in strength of this dipolar source can be explained if we assume that: (a) the later activity of the first perirolandic dipole can represent the inhibitory phase of a “primary response”; (b) two different clusters of cells generate the opposite activities of the tangential perirolandic dipole. An additional finding in our model was that two different perirolandic dipoles contribute to the centro-parietal N20 potential generation. Received: 5 August 1997 / Accepted: 26 November 1997     

Language processing from the perspective of electrical stimulation mapping

ABSTRACT

Electrical Stimulation (ES) is a neurostimulation technique that is used to localize language functions in the brain of people with intractable epilepsy and/or brain tumors. We reviewed 25 ES articles published between 1984 and 2018 and interpreted them from a cognitive neuropsychological perspective. Our aim was to highlight ES as a tool to further our understanding of cognitive models of language. We focused on associations and dissociations between cognitive functions within the framework of two non-neuroanatomically specified models of language. Also, we discussed parallels between the ES and the stroke literatures and showed how ES data can help us to generate hypotheses regarding how language is processed. A good understanding of cognitive models of language is essential to motivate task selection and to tailor surgical procedures, for example, by avoiding testing the same cognitive functions and understanding which functions may be more or less relevant to be tested during surgery.