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• • """"")' PHYSIOLOGICAL i>.fECHANISMS, ANALYSIS AND BEHAVIORAL SIGNIFICANCE OF THE ELECTRODERMAL RESPONSE \ \ ' \ . \ \ FINAL REPORT \ . ·-· -····-..!. .. \ \ \\ ~~ ~ \ :• \ Section 12 Vascular Effects Upon Skin Potential. 82 13 References • 89 ) • PHYSIOLOGICAL ~lECHANLS~IS, ANALYSIS Ai'\D BEHAVIORAL SIGNIFICANCE OF TilE ELECTRODER:-..1AL RESrO~SE 1. L'iTRODUCTION " This project was directed toward exploration of physiological mechanisms underlying the electrodermal response in the hopes of establishing a rational basis for quantitative treatment ?f this measure as a behavioral indicant. A further objective was to gain a better understanding of the adaptive function of electrodermal activity. It was presumed that the role of such activity in our "psy.chological" life can be understood if sucl;l behavior is regarded as essentially a biological adaptation, modified to fit a social structure. Thus, if electrodermal activity is associated with profuse palmar sweating, and this can be shown to be defensive in function, one has grounds for interpreting such activity as a sign of fear or anxiety. If, on the other hand, other forms of electrodermal activit ' y facilitate' manipulation or exploration, one would put an entirely different interpretation on its ap1=earance. For example, if, in a situation which is potentially threatening, one notes evidence of the manipulative type of electrodermal activation, it would seem appropriate to conclude that the subject ' is engaged in copL1.g behavior rather than that he is beset with alarm. The first portion of this three-year program was devoted primarily to physiological investigations. ·An assortment of evidence, covered in the interim reports, helped to round out the partially elaborated physiological model of the electrodermal system. Among these experiments were microelectrode observations on sweat ducts and the areas between the ducts, confirmation of potential responses from the nail bed, study ) 2 ·-...... electrolytes on electrodermal responses, and finally continuing studies on the sweat 1 I reabsorption mechanism and its reflex control. These v<.rious findings, when integrated with other experimental evidence, lead to the formulation of a model in whkh sweat reabsorption played a prominent role and in which such activity was . reflected in the recovery limb of the skin conductance or resistance response. According to this model the sweat gland has a dual function; if it secretes profu.sely, the skin surface becomes well-hydrated and resilient and is thus protected against abrasion. In a biological sense The image is a graphical representation of a vault door, with glowing blue accents, possibly symbolizing security or secrecy. To the right of the vault, white text on a black background displays the title "THE BLACK VAULT" in a stylized script, followed by descriptive text about the document's origin. The text explains that the document was obtained from "The Black Vault," an online database of declassified government documents, specifically referencing the MKULTRA/Mind Control Collection, which contains over 20,000 pages declassified by the Central Intelligence Agency (CIA). The text concludes by providing a URL for downloading the collection. in which such activity was . reflected in the recovery limb of the skin conductance or resistance response. According to this model the sweat gland has a dual function; if it secretes profu.sely, the skin surface becomes well-hydrated and resilient and is thus protected against abrasion. In a biological sense the animal is now able to scamper over the rough ground av-~ay f:rom danger without undue mechanica\ damage to his contact areas. For fine manipulation, however, as may be involved in exploration and . ~ ... . .assessment of cbjects irt the immediate surrounds, tactile requirements arc such ) that the optimum level of surface moisture is somewhere intennediate bet\veen dry and wet. It was supposed that regulation of surface r:noisture at light to moderate hydration is largely a function of the activity of the sweat reabsorption mechanism. Observation of conditions under which reflex sweat .reabsorption occurs led to the ~onclusion that this mechanism goes into action in preparation for "manipulative" tasks. This activity is reflected in increased positive~going" skin potential responses and in acceleration of recovery of COfl:ductance responses. The m&jor effort of thls investigation was then directed toward the ~laboratlon of this recovery limb measure, in terms of its measurement, its relation to amplitude, tc .. conductance level, and to behavioral state, and to the comparison of its discriminating strength with :hat of other electrodermal measures. TI1is report summarizes progress to date. It is broken into a series of separate topics rel<:>.ted to these objecti\'es. ) ------ •- .. ;, '"' :1nnrnnrhte to render as complete a '~-~~ ,..~-,"' • 3 picture as possi.l::le within this report. One full-length paper, "TI1e information con- tent of the recovery limb of the electrodermal response" (in press) has been in part supported by this contract and is included as part of :his final report since it summarizes the approach and findings in an optimal manner. Iri addit.ion to th'c various sections on the recover}· limb, there is one on the relation of vascular changes to skin potential shifts at the surface. Although some of this material was described in an interim report, it has now been completed and com posed as an integrated manuscript to be submitted for publication, and is, therefore, included in toto in this report. ) ) ·e 5 coupling time constant of 10 seconds, the loss of sensitivity becomes negligible for all but the very slowest recovery The page contains two lines of sans-serif text: "PHYSIOLOGICAL MECHANISMS, ANALYSIS AND BEHAVIORAL" and "SIGNIFICANCE OF THE ELECTRODERMAL RESPONSE." There is a stamp resembling a stylized "FB" in the upper right corner. Towards the bottom of the page, the words "FINAL REPORT" are handwritten within a partially drawn schematic or diagram that appears to be some form of graph or waveform. There are no photographs, forms, tables, or specific experimental details visible. report, it has now been completed and com posed as an integrated manuscript to be submitted for publication, and is, therefore, included in toto in this report. ) ) ·e 5 coupling time constant of 10 seconds, the loss of sensitivity becomes negligible for all but the very slowest recovery limbs. Recovery rate was found to be capable of distinguishing between many be- havioral states, even when response amplitude or response frequency could not. Thus, to name a few, it distinguished: orienting responses to a light flash from responses to the same flash when it took on signal properties, responses to an alert~g signal from those to a task-execution signal, the resting state from various task situations, mirror tracing from bad.-ward counting or cold pressor exposure, problem solving from perceptual or psycho-motor behavior, a deception task from a reaction time task. In the course of these comparisons it was found that recovery :rate be- , . . ~. I came slower with habituation, even in a deception task, a::1d that it was also slowed by the entry of a fright stimulus into a task situation. It failed to distinguish a decep- ) • tive response from a non-deceptive response in a given seri~s of queries when differ- ences were comp:1red across the entire population, but individual. subjects did frequently show a clifference. The design of this experiment was unfortunately aimed at group analysis and the number of deceptive responses for a given subject was insufficient to evaluate this individual effect statistically. , An overview of the effect of the various task and stimulus situations upon electro· dermal recovery rate indicates that acceleration of recovery reflects mobilization for goal-oriented performance. That the determining factor was not general activation I per se was evidenced by the slow recovery accompanying a cold pressor exposure, shown by other electrodermal indicants to be as activating as were performance tests ) associated with rapid recovery. 6 The recovery measure for a given individual in a standard situation wos sho\'m to be relatively stable over a period of 5 consecutive weeks. There were large characteristic individual differences between individuals even though they changed in the same direction when changing behavioral conditions. Efforts to find a behavioral trait associated wit:.1 recovery rate were generally unsuccessful although fast recovery in a standard task (reaction time) was found to be associated with low anxiety (SAQ), and with a tendency to The page contains a table of contents or index, listing sections and their corresponding page numbers. A curved line graph is depicted, possibly representing data or a process, spanning sections 10 and 11. Section 12 is titled "Vascular Effects Upon Skin Potential" and is linked to page 82. Section 13 is titled "References" and is linked to page 89. The document appears to be from an official report, with the word "Section" and "Page" serving as column headers. There are no photographs, handwritten annotations, or stamps visible. between individuals even though they changed in the same direction when changing behavioral conditions. Efforts to find a behavioral trait associated wit:.1 recovery rate were generally unsuccessful although fast recovery in a standard task (reaction time) was found to be associated with low anxiety (SAQ), and with a tendency to maintain electrodermal response withO'lt habituation during a reaction time series. This was seen as further evidence supporting the interpreta- tion of fast recovery as reflecting mobilization for goal-directed behavior, since these same subjects habituated to a series of non-signal tones just as fast as did subjects with slow recovery rate. It is still uncertain as to whether the difference in recovery rate betw·een problem solving and simple perception indicates a specific difference in ) the effects of cognitive and perceptual behaviors on recovery, or_whether this simply means that the problem-solving task was associated with higher an."Ciety. An examination of the relationship of recovery rate to other parameters of the response showed it to have a low negative correlation with amplitude, that is, responses of higher amplitude in a given behavioral state tended to have slightly slower recovery. When measured between different behavioral states, howev-~r, there was ·often a tendency for the reverse to be true. In view of the evidence showing that mobilization for goal· directed behavior is associated with faster recovery, this observation probably reflects the fact that mobilization for task perlorrnance frequently causes an increase in activation resulting in electr::>dennal responses of high amplitude. This same conside_ro.tion probaply explains the fact that recovery rate is related (positively) to skin conductance level in ) --. - - ,_ • 7 During the coLLrsc of a comparison of the discriminating strength of the recovery rate measure with other electrodermal measures, a new frequency measure was devised. TUs measure is different from other measures of !'GSR frequency" or "count" in that it examines, for any given task or epoch, not the total number of re~ ' sponses but rather the maximum frequency displayed i.n a "burst" of three consecutive responses. This measure, termed f max, demonstrated a surprising strength in dist~guishing between stimulus conditions, although not the same conditions as were distinguished by recovery rate. Thus f max distinguished the deceptive response from listening to instructions, but recovery rate was not able to do so. Contrariwise, recovery rate d:.stinguis!1ed perception from problem so:ving while f max did not. The highest· f The document is a typed page with a title "PHYSIOLOGICAL MECHANISMS, ANALYSIS AND BEHAVIORAL SIGNIFICANCE OF THE ELECTRODERMAL RESPONSE" and an introduction section numbered "1.". There are no photographs, handwritten annotations, or official stamps visible. There are no forms, diagrams, schematics, organizational charts, or tables. There are no visible redactions or obscured content. The visual content consists solely of the typed text of the document's introduction. This page is a scanned document with text that appears to be typed. There are no photographs, handwritten annotations, signatures, or official stamps visible. There are also no forms, diagrams, tables, or other structured data. The page contains a small number '2' at the top center, likely a page number. There are also what appear to be redactions or obscured content at the bottom right of the page, indicated by lines of dots. No specific experimental procedures or equipment are visibly depicted. between stimulus conditions, although not the same conditions as were distinguished by recovery rate. Thus f max distinguished the deceptive response from listening to instructions, but recovery rate was not able to do so. Contrariwise, recovery rate d:.stinguis!1ed perception from problem so:ving while f max did not. The highest· f max and the fastest recovery rates were both found during the reaction ) time test, but the level off max reached by any subject during this task, unlike recove1y rate,. bore no relation to his trait anxiety. A companion study, one directed at the physiological basis of skin potential levels and changes, demonstrated that a one minute engorgement of cutaneous vessels produces a slow negative shift and upon release of the cuff a sudden positive shift. I . With arterial occlusion these potential shiits were opposite in direction and greater in magnitude. Although changes were generally not over 0.5 mv they raise the possibility that vasomotor responses may be accompanied by surf2.ce potential waves. Whether these shifts were mediated by an effect of the vascul<J.r state on sweat gland potentials or whether they represent changes in vascular potentials remains to be determined. \ • 8 3. ON THE ~lEASURE}.'lENTOF ELECTRODER~1AL P..ECOVERY RATE: RATIONALE The measurement of electrodermal recovery rate may be approached in several ways, all of which have in common the assumption that"rhere is an intrinsic recovery rate characteristic which may be the same for waves of greatly varying amplitudes. An example of such a condition is that for the exponential curve in which a characteristic time constant or constant may be common to all members of a family of curves of rat~ different amplitudes. Darrow (1937) concluded that the recovery limb of the skin resistance res?onse (SRR) is exponential in form, and additional evidence, to be pre· sented here, supports this interpretation. Methods for evaluating the rate constant of the electrodermal recovery limb are )· suggested from examination of the differential equation describing the exponential rela tion. The process described by this relation is one in which a variable changes at a rate, dE/ dt, which at any instant is a linear function of the magnitude of that variable. Thus, for the case-of voltage change in a condenser discharge . . 1) which may signify, for example, that the voltage drops by 5% per second, in which case .05 is the constant characteristic of such a process. Rate The page contains a numerical identifier "3" at the top. The main content is text, describing a report and a manuscript. There are no photographs, handwritten annotations, stamps, forms, diagrams, tables, or redactions visible on this page. The page primarily consists of typed text, detailing the content and structure of a report and a related manuscript. instant is a linear function of the magnitude of that variable. Thus, for the case-of voltage change in a condenser discharge . . 1) which may signify, for example, that the voltage drops by 5% per second, in which case .05 is the constant characteristic of such a process. Rate Constant The integral of the above expression provide::; the common express ion for exponential decay, namely 9 -l where E is the starting level and E is instantaneous voltage at time, t; k is the rate 0 constant (rc). If E is deca.ying to zero as its asymptote, -/rt ;::-- _ r:- 3) .,..._ - ;::.. o e When t = 1/k, E == E /e• that is, it equals 37% of its original value. This time, which 0 is equal to the reciprocal of the rate constant, is called :he time constant {tc) and, like the rate constant, is characteristic of the process and independent of amplitude. All curves having this same ·characteristic regardless of their starting point may be superimposed upon the. same large exponentia.l curve. Thus, to the extent that the electrodermal recovery Jimb is exponential, it may be matched to an exponential curve of the same rate constant. This is the basis of the use of an overlay method ) for determining the time constant by curve.matching as described in section 6. Half-Time From equation (2) it can be shown that decay hall-time, that is, the time taken for decay to become 50% completed, is equal to 0. 7 tc and is a constant for all waves having the same time constant, independent of their amplitude. This measure, the recovery half-time, represents a second means of expressing reco.v ery rate and is also described in section 6. Logarithmic Writeouts Equation (2) represents a means of determining the degree to which the recovery limb fits an exponential curve, Expressed in common logarithmic form, ) t k ~ 4) I f - /_ ;::- -· • 10 from which it follows :.hat a writcout kJ.Ving log;J.rithmic vertical compi:cssion should give for exponential curves. a straight line whose slope is a- k/2. 3. The upper trace in Figure 1 is a writeout of an exponential curve obtained by capacitor discharge :1nd a recording of J. few skin conductance responses. fu.seline of the skin conductance trace has been adjusted so that responses are recovering to approximately zero voltage. Below are is a- k/2. 3. The upper trace in Figure 1 is a writeout of an exponential curve obtained by capacitor discharge :1nd a recording of J. few skin conductance responses. fu.seline of the skin conductance trace has been adjusted so that responses are recovering to approximately zero voltage. Below are the same waves recorded through a lot,:rarithmic coopression circuit. Note that the portion of the recovery limb which is exponential in fonn starts about one second after respons~ peak. The slope of the linear portion of the logarithmic recqvery limb is proportional to the rate constant provided the asymptotic voltage is zero. Since. this is not ~o. such a method cazmot be used dir~ctly. One may, however, apply the second derivative to achieve this end. J'fhe time de-rivative of equation (1) is which may be written: -- 5} or Integrating, t c. _)r which indicates that the first derivative of an exponential curve is also e.~ponential as is its second derivative. The slope of the log-compressed writeout of the first . derivative is then proportional to k and unlike the case for the primary (DC) write· ) out, the curve, as required, decays toward zero becJ.use of the capacitative coupling · '-- ~":~ •.. .,..;~,.,,..,,'" hu Plc>r_rronic conversion. Since • • lO:l • ....... -:----:"""':' ;,. .,. __ --;-•• ...-..... 'Or-~-:--, ~• ~~---·-_. ~: . ; .. .: -·· - -~ - . · . . ~ . . .. . ~ .. . .. .... I '.. -~-. ·~-=-··.i . ; : : ; . ~· p ·-~; .- ••••'"•rr··-•• - , .. ~ •-......... ,_, _____ ~-~- :.::.:.., ~~- :·~;I:~~--~~~~;-~;:;_;··; -0~~J\.;J:~~~~ :~~~~··..:....._ ) Figure 1. Upper trace: direct writeout of a condenser discharge (CAP) and skin conductance trace (SC). Paper speed 1 mm/ sec. Lower trace: same as upper but with logari:hmic compression. Figure 2. Diagram of method for measuring the rate :::onstant by tan A/H. \ 11 2.'3 one is tempted to produce a writeout of d log E1/dt to obtain an amplitude reading directly proportional to the rate constant. Unfo~tunately, d log E~/dt often has such a low magnitude in the exponential portion of the recovery limb that its analog form cannot serve reliably as the expression for the rate constant. A similar problem ·arises if one attempts to deten:nine the rate constant from the log-compresse~ first derivative curve (log d E/dt) by manual measurement of The document page contains mainly typed text with a page number "5" at the top and a bullet point immediately above it. There are also instances of faint, handwritten annotations, such as a slight curved line on the left margin near the top, and a similar curved line near the bottom. The text discusses experimental findings regarding recovery rates in different behavioral states and tasks. There is no visual evidence of photographs, diagrams, forms, tables, stamps, or redactions on this page. The page is a scanned document, likely a declassified report, with faint blemishes and uneven lighting. At the top, there are two dark circular marks, likely from the scanning process. A single page number, "6", is printed near the top center. The text is typed and appears to be a continuation of a research paper or report, discussing recovery measures and behavioral conditions. There are no visible handwritten annotations, stamps, forms, diagrams, tables, or redactions. The nature of the document suggests it could be related to experimental data or findings, but no specific experimental procedures or equipment are visually depicted. a low magnitude in the exponential portion of the recovery limb that its analog form cannot serve reliably as the expression for the rate constant. A similar problem ·arises if one attempts to deten:nine the rate constant from the log-compresse~ first derivative curve (log d E/dt) by manual measurement of the tangent of the acute angle produced between the linear portion of the recovery limb· and baseline • ........, Second Derivative Yet another method may be derived from the se.cond derivative form. From equation (5) _./1 ·- ~ ~I 'Thus, one may determine the recovery rat'~ constant by calculating at any point on the recovery limb the quotient of the second derivative ..;- the first derivative. In practice the method is not too feasible because tli~ magnitude of E11 is so low in the exponential. region of the recovery limb that it frequently is excee:ied by the noise level of the trace, which becomes rather high for the analog second derivative. Amplitude-Slope Method Another solution is one which requires an amplitude measure as well as a slope. From equaticn (1), it is seen that ) ]""/ 12 the slope of E, or its first derivative. TI1is is a most useful expression. From it, one can obtain the value for k by taking the slope and amplitude of any point on the exponential portion of the decay (Figure 2). TI1c slope is tan A. Tn practice it must be chosen at a point at or beyond the inflection point on the recovery limb. Because a - measurement of wave amplitude would seem to be more precise and because such a measurement could be used independently as an index of responsivity, a test was rnade.of the relation of H to h (Figure 2), i.e., of peak amplitude to the amplitude at the inflection point. TI1e product-moment correlitions for 20 responses on each of 6 subjects were: • 97, • 99, • 99, • 99, • 99, and • 96. Thus a convenient substitute measure for the rate con. stant is . A io!J 6) !-I ) This method showed a correlation of 0. 81 ~vith measurements made by the templ.ate metho~ on the same 66 responses. In making the slope measurement, a line is drawn . . parallel to the recovery limb at its inflection point. The acute angle at the intersection . of this line with the horizontal is measured and The page is visually sparse, primarily consisting of typed text. At the top, there's a horizontal line indicating the top margin, and to the right, the number "7" is centered, likely a page number. Circular marks appear near the top margin, possibly ink blots or imperfections from the scanning process. The left margin has a vertical line and a curved bracket-like mark. There are no photographs, stamps, handwritten annotations, diagrams, forms, or tables visible on this page. The content is exclusively presented as typewritten text. 0. 81 ~vith measurements made by the templ.ate metho~ on the same 66 responses. In making the slope measurement, a line is drawn . . parallel to the recovery limb at its inflection point. The acute angle at the intersection . of this line with the horizontal is measured and its tangent obtained from tables~ Anothe I relation in conjunction with this method penn its a relatively simple approach to auto- mated calculation of the rate constant. The peak slofe of the ascending limb is found to be linearly related to the ma..ximum amplitude of the primary writeout (Edelberg, 196: A validation check of this relationship in the present investigation confirmed this. Measurement of 44 responses having uncomplicated ascending limbs gave a correlation of 0. 94 between the two measures. Hence one may substitute for I-I the maximum first derivative o: the ascending limb, and for t:D.n A the maximum first derivative of the ) 13 ' 4. ON THE ~1E.c\SURE~1El\'T OF ELECTRODER:\1AL RECOVERY RATE BY I PREFERRED :WffiTHODS: TESTIL\G At\TI CO~!PARISON A) Logarithmic Compress ion In the discussion of the various means of computing electrodermal recovery rates it was shown that the first derivative of the logarithmic writeout of ~he recovery limb is directly proportional to the rate constant. This is true when logarithmic com- pression is accomplished by electronic means, but only if the wave is recovering to a zero voltage level. In such cases, the region of the recovery limb immediately following the peak (by about 1 second) is linear, and it is this portion whi~h should reflect the rate "constant." Unfortunately the DC-recorded trace rarely recovers to zero voltage as its asymptote. Since the first derivative does have essentially a zero ) voltage asymptote, logarithmic compressiofl. of such a writeout should offer a linear section of the recove.-:y limb whose slope is proportional to the rate constant. Un- fortunately, tl'.e electronically ·differentiated recovery slope is often of such low amplitude that log compression and manual measurement pose a problem in accuracy. It has been shown, however, (Section 5) that the rec ..' yery rates of electrodermal responses recorded with capacitance coupling are highly correlated with those computed from a DC record provided the coupling has a time constant of 6 seconds or longer. Such condenser-coupled records do approximately satisfy the requirement that the asymptotic voltage is zero. If a record of this kind is subjected to responses recorded with capacitance coupling are highly correlated with those computed from a DC record provided the coupling has a time constant of 6 seconds or longer. Such condenser-coupled records do approximately satisfy the requirement that the asymptotic voltage is zero. If a record of this kind is subjected to logarithmic com- pression, the recovery limbs should show a linear portion whose slope is proportional to the rate constant (Figure 3). This ~tudy examined such records to determine the ) degree to whL::h the rate measure computed from their slopes were correlated with the • 13a DC 6-sec _) Log 6-sec Figure 3. Recording of skin conductance through normal DC (upper), capacitance coupling with a 6-second time constant (middle), and log compression of ::he 6-second Wliteout (lower). Paper speed l1nm per second, nonnal size. ) • Method ' I Ins trumcnta tion Skin conductance was recorded on a Beckman Dynograph with direct coupl- ing (channel 1). The pen (1) output was coupled to the 2 megohm input of another DC channel through a 3-microfarad condenser to obtain the o-second time constant. The pen (2) output of this second channel was placed in series with a 220 K resistor and a -silicon diode (fexas Instruments G-129). The voltage developed across the diode is a logarithmic. representation of the pen (2) output (Kahn, 1962). This voltage was fed L'lto a third channel of the Dynograph and, with zero input into channel (1), and the recording completely restored to baseline, the zero position of pen 2 was adjusted until the voltage across the diode was forNard_ biassed by i). 25 volt: Polarity was arranged so th.at an electrodermal response produced increasing forward bias on the ) diode. Measuring Technique A straight line is drawn parallel to the linear portion of the recovery slope in d.- the region immediately after the peak of the response (Figure 4). On can then I' measure the acute angle (A) which this line makes with the horizontal, and obtain its tangent from tables. This va.lue. is directly proportional to recovery rate con~tant. An alternative method is to use the L·shaped scale shown in Figure 4. The ver·t~ ~al limb is set so that it passes through the intersection of tl:e slope with the upper edge of the paper channel. The horizontal distance from this point to the intersection of the slope with the bottom edge of the paper The page displays printed text with a number "8" at the top center. It includes a section titled "ON THE MEASUREMENT OF ELECTRODERMAL RECOVERY RATE: RATIONALE". There is a handwritten mathematical equation, "dE/dt = -kE", as well as a circled "1)" next to it. Another handwritten phrase, "Rate Constant", appears below the equation. The page also has a drawing consisting of two horizontal lines with short vertical lines forming a textured pattern, resembling a border, at the top and a large curved bracket on the left side. There are no photographs, stamps, forms, diagrams, tables, or redactions visible on this page. This page is a typed document with several handwritten annotations and a numbered equation. The top of the page has a page number "9". There are two drawn lines extending from the left margin, one enclosing the number "3)" and