Event-related brain correlates of associative learning without awareness.

Controversy exists about whether associative learning occurs without awareness. In an earlier study using subthreshold (subliminal) stimuli, we reported evidence that such learning could occur as measured by event-related brain potentials [ERP; Cons. Cognit. 6 (1997) 519]. In the present study, we extend these findings by changing several aspects of the methodology in order to provide a more stringent test of this effect and to examine its generality. We used two matched words (murder and cancer) as conditional stimuli (CS); a 100 dB white noise blast as unconditional stimulus (US); a CS-US interval of 3 s; and a full-factorial design with CSs counterbalanced. The conditioning-acquisition phase occurred when the CSs were perceptually unconscious, as confirmed by a subsequent behavioral task. The conditioning-acquisition and postconditioning-extinction phases were examined for ERP evidence of associative learning. The clearest and strongest evidence for associative learning without awareness was observed in the ERP component measures (up to 1 s, poststimulus) in the postconditioning-extinction phase. The CS+ was significantly more positive than the CS- in the P3b-LP component region, which is highly consistent with the results of our earlier study. Differences also were observed in the P1-P2 components. In an unexpected finding, we observed a significant positive slow potential shift for the CS+ in the region between 1 and 3 s poststimulus. We discuss these results and their implications for our understanding of associative learning and awareness.

Kinetics of removal of carbonyl sulfide by aqueous monoethanolamine.

The kinetics of the reaction between carbonyl sulfide and aqueous monoethanolamine (MEA) were studied over a range in temperature (298-348 K) and amine concentrations (5-20 wt%) using a wetted-sphere absorber. The experimental data were interpreted using a zwitterion mechanism. The key physicochemical properties needed to interpret the data are the solubility and diffusivity of COS in the aqueous amine solution. These properties were estimated using the N2O analogy method. Experimental values of N2O solubility were correlated using an extended scaled-particle model, and the measured N2O diffusion coefficients were correlated using a modified Stokes-Einstein equation. Solution densities and viscosities were also measured and correlated in this work. On the basis of the zwitterion mechanism whose rate-limiting step was the deprotonation of a zwitterion, the Arrhenius relationship between the third-order rate constant and the temperature was well correlated with an absolute mean deviation of 0.3%. It could be thus concluded that the overall reaction rate was first-order in the COS concentration and second-order in the MEA concentration.

Subliminal visual oddball stimuli evoke a P300 component.

OBJECTIVE: To provide evidence that a P300 component can be elicited by subliminal stimuli in an oddball paradigm. METHODS: The words LEFT and RIGHT were presented in a frequent-rare ratio (80-20%), counterbalanced between subjects. Stimuli were presented at the objective detection threshold (d'=0, via unmasked 1 ms presentations), a stringent measure for detecting any conscious perception. RESULTS: A significantly larger amplitude component was found for rare vs. frequent stimulus presentations across electrodes Fz, Cz, and Pz using both a broad 200-900 ms window (F(1,27)=5.75, P<0.012, eta(2)=0.18; one-tailed), and a more narrow 400-760 ms window defined using principal component analysis (F(1,27)=10.10, P<0.002, eta(2)=0.27; one-tailed). No significant component latency effects were found. An analysis of the conscious perception index (d') and the oddball effect (rare-frequent amplitude difference) revealed a negative relationship, further supporting the contention that conscious perception does not account for the finding, and suggesting that any conscious stimulus detection may inhibit this subliminal effect. CONCLUSIONS: Results provide evidence that an endogenous component can be elicited by undetectable subliminal stimuli in an oddball paradigm. Implications are discussed for comparing conscious and unconscious information processing, unconscious learning, and the measurement of ERPs to subliminal stimuli.

The primary process and the unconscious: experimental evidence supporting two psychoanalytic presuppositions.

The authors report on two experiments designed to test an important feature of the primary process: unconscious categorisation by attributes rather than by relations. These experiments were designed to provide support, independently of the clinical situation, for the presupposition of a psychological unconscious and for the presupposition that unconscious mentation is organised along primary-process lines. Their results were encouraging. They found that (1) unconscious similarity judgements could be made; and (2) these judgements were based on attributes (a primary-process mechanism) rather than relationships (a secondary-process mechanism). This independent evidence, obtained in controlled experimental studies supporting two fundamental psychoanalytic presuppositions, should be welcome news to psychoanalysts, given the continuing criticism from many quarters that basic psychoanalytic ideas lack independent validation. This paper begins with an overview of the primary processes with a special focus on the role of categorisation by attribute, the particular aspect of primary process explored in this study. Next a brief history of previous empirical investigations of primary process is given, following which the current experiments are presented.

Music absorption and hypnotizability.

The present study investigated differences between high (N = 15), medium (N = 20), and low (N = 16) hypnotizable Ss' involvement in imaginative versus nonimaginative music. Ss were first screened for hypnotizability with the Harvard Group Scale of Hypnotic Susceptibility, Form A (Shor & E. Orne, 1962). In a second session presented as a study of music appreciation, Ss listened to classical music of high and low rated music imaginativeness. Ss' involvement was indexed by absorption, imagery elaboration reported in open-ended essays, and reaction time to a pure tone. High hypnotizable Ss reported more absorption than low hypnotizable Ss, regardless of the imaginativeness level of the music. Ss reported more imagery elaboration in the imaginative than in the low imaginative passages. High hypnotizable Ss tended to differ in their imagery elaboration in response to the imaginative passages but not in response to the nonimaginative passages. Reaction time results were nonsignificant. No sex differences were found. Medium hypnotizable Ss were indistinguishable from both high and low hypnotizable Ss. The findings are generally compatible with J. R. Hilgard's (1970, 1974) construct of imaginative involvement.

Goal-directed fantasy, hypnotic susceptibility, and expectancies.

We conducted an initial screening session in which hypnosis was presented as a "test of imagination" and administered with other imagination measures. In a second session, we instructed high- and low-hypnotizable subjects to imagine along with suggestions but to resist responding to motoric suggestions. Subjects received either instructions to use goal-directed fantasies (GDFs) or no facilitative instructions. Sizable individual difference effects were secured. Hypnotizable subjects exhibited more suggestion-related movements and reported greater involuntariness than did low-hypnotizable subjects. With GDF instructions, low- and high-hypnotizable subjects reported equivalent GDF absorption and frequencies. However, hypnotizable subjects exhibited greater responsiveness and reported greater involuntariness than did those low in hypnotizability, even when their GDFs were equivalent. Thus, no support was generated for the hypotheses that sustained, elaborated suggestion-related imagery mediates response to suggestion (Arnold, 1946) or that absorption in suggestions is of particular importance for low-hypnotizable subjects (Zamansky & Clark, 1986). Our finding that measures of response expectancy paralelled responding and reports of nonvolition support the hypothesis that expectancies mediate the relation between imagination, involuntariness, and responding (Kirsch, 1985; Spanos, 1982). Hypnotizable imagining subjects in the study discussed here exhibited greater responsiveness than a comparable sample of subjects did in a previous countersuggestion study (Lynn, Nash, Rhue, Frauman, & Stanley, 1983) in which no attempt was made to foster an association between imagining and involuntary responding in the initial screening session.

Localization of a macrophage chemokinetic factor on neoplastic cells.

A rabbit antiserum was produced against a high-molecular-weight fraction (360,000) of murine Lewis lung carcinoma (LLC)-conditioned media. This fraction contained a factor that increased the rate of random migration (chemokinesis) of activated macrophages (M phi) in male C57BL/6J mice. The specificity of the antiserum was demonstrated by the ability of the antiserum to absorb the chemokinetic activity from tumor-conditioned media. Immunofluorescence studies demonstrated cell surface localization of antigenetically similar material on the LLC, Ehrlich ascites cells, MCA9/14 and MCA64/8 mouse fibrosarcomas, and MBT-2 mouse bladder carcinoma. The antiserum further indicated the presence of the chemokinetic factor (CKF) on the surface of peritoneal M phi previously exposed to tumor media. The CKF was observed on approximately 90% of the Corynebacterium parvum-activated M phi and of the M phi activated by maleic anhydride-divinyl ether copolymer (fraction 2), on 10% of the oyster glycogen-elicited M phi, and on 0% of the unstimulated M phi. these data support the concept that the CKF is a common surface marker of neoplastic cells and that it is bound by activated tumoricidal M phi.

Characterization of a macrophage chemokinetic factor in tumor cell culture media.

Media conditioned by tumor cells were studied for the presence of factor(s) that increase the rate of random migration (chemokinesis) of Corynebacterium parvum-activated macrophages. A capillary tube assay was developed and utilized to expediently monitor the chemokinetic activity of macrophages incubated in whole and fractionated media. Media conditioned by six different syngeneic and allogeneic mouse tumor cell lines demonstrated significantly higher chemokinetic activity than unconditioned or normal fibroblast conditioned media. The chemokinetically active component of the Lewis Lung conditioned media was found to be a trypsin sensitive, heat stable, high molecular weight (300,000-480,000 dalton range) factor that had no chemotactic (directional migration) activity. Pyran-activated macrophages also responded chemokinetically to the Lewis Lung factor while oyster glycogen and thioglycolate-elicited macrophages did not. The similarity and differences between the physical properties of the chemokinetic factor, other migration stimulating factors, and tumor-associated proteins are discussed.

Inhibition of host resistance by nutritional hypercholesteremia.

Previous experiments showed that nutritionally induced hypercholesteremia in mice caused an increase in susceptibility to coxsackievirus B, with a marked suppression of cellular infiltrates in infected tissues and an increased mortality. The present studies demonstrated that a hypercholesteremic diet was associated with an inhibition in host resistance as measured by susceptibility to Listeria monocytogenes infection and the growth of two transplanted syngeneic murine tumors. Moreover, the ability of Corynebacterium parvum to induce regression of a transplanted methylcholanthrene-induced fibrosarcoma was inhibited in hypercholesteremic hosts, as was the histiocytic infiltration normally accompanying C. parvum inoculation. In contrast, the peritoneal macrophages from C. parvum-treated hypercholesteremic mice were indistinguishable from similarly treated macrophages from normal mice with respect to their in vitro tumoricidal activity and the presence of a cell surface antigen associated with activated macrophages. Hypercholesteremia was also associated with a decreased antibody response to sheep erythrocytes in vivo, but dit not appear to exert a detrimental effect on B- or T-cell blastogenesis when tested in vitro. The findings that the hypercholesteremic diet was associated with an impairment in the host immune response and increased susceptibility to viral, bacterial, and tumor cell challenge are discussed with respect to virus-lipid interactions in the pathogenesis of atherogenesis and diabetes mellitus.

Potential mechanism of macrophage-mediated tumor cell cytotoxicity.

Activated macrophages have been shown to inhibit the incorporation of 125IUDR into the DNA of Lewis lung (LL) tumor cells and to lead to the cytotoxicity of these target cells. Despite this apparent inhibition of DNA synthesis, the increase in the number of LL cells cultured with activated macrophages paralleled that of LL cells alone for the first 18 hours of culture (approximately one doubling of cells). To resolve this paradox, the DNA content of LL cells, which were cultured with activated macrophages for 16 hours, was analyzed by flow microfluorometry. These experiments indicated that subsequent to co-culture with activated macrophages, LL cells with a 50% reduction in their normal DNA content could be detected. Furthermore, after a 2-hour incubation with colcemid, a greater than 95% reduction in metaphase cells occurred in LL cells cultured with activated macrophages. However, dividing nuclei without chromosome condensation appeared to be a prominent feature of these cultures. This would suggest that the genotypic or phenotypic program for cell division in the tumor cells is such that under these unique circumstances of tumor cell-activated macrophage interaction, cell division can proceed in the absence of DNA synthesis. We suggest that this aberrant division may be related to the lethal event which leads to activated macrophage-mediated tumor cell cytotoxicity.