Neuroscience of Pavlovian conditioning: a brief review

Proposing a Framework for the Restorative Effects of Nature through Conditioning: Conditioned Restoration Theory

Natural environments have been shown to trigger psychological and physiological restoration in humans. A new framework regarding natural environments restorative properties is proposed. Conditioned restoration theory builds on a classical conditioning paradigm, postulating the occurrence of four stages: (i) unconditioned restoration, unconditioned positive affective responses reliably occur in a given environment (such as in a natural setting); (ii) restorative conditioning, the positive affective responses become conditioned to the environment; (iii) conditioned restoration, subsequent exposure to the environment, in the absence of the unconditioned stimulus, retrieves the same positive affective responses; and (iv) stimulus generalization, subsequent exposure to associated environmental cues retrieves the same positive affective responses. The process, hypothetically not unique to natural environments, involve the well-documented phenomenon of conditioning, retrieval, and association and relies on evaluative conditioning, classical conditioning, core affect, and conscious expectancy. Empirical findings showing that restoration can occur in non-natural environments and through various sensory stimuli, as well as findings demonstrating that previous negative experience with nature can subsequently lower restorative effects, are also presented in support of the theory. In integration with other existing theories, the theory should prove to be a valuable framework for future research.

Dissociable learning processes in comparative psychology

Comparative and cognitive psychologists interpret performance in different ways. Animal researchers invoke a dominant construct of associative learning. Human researchers acknowledge humans' capacity for explicit-declarative cognition. This article offers a way to bridge a divide that defeats productive cross-talk. We show that animals often challenge the associative-learning construct, and that it does not work to try to stretch the associative-learning construct to encompass these performances. This approach thins and impoverishes that important construct. We describe an alternative approach that restrains the construct of associative learning by giving it a clear operational definition. We apply this approach in several comparative domains to show that different task variants change-in concert-the level of awareness, the declarative nature of knowledge, the dimensional breadth of knowledge, and the brain systems that organize learning. These changes reveal dissociable learning processes that a unitary associative construct cannot explain but a neural-systems framework can explain. These changes define the limit of associative learning and the threshold of explicit cognition. The neural-systems framework can broaden empirical horizons in comparative psychology. It can offer animal models of explicit cognition to cognitive researchers and neuroscientists. It can offer simple behavioral paradigms for exploring explicit cognition to developmental researchers. It can enliven the synergy between human and animal research, promising a productive future for both.

Structural imbalance promotes behavior analogous to aesthetic preference in domestic chicks

Background

Visual images may be judged ‘aesthetic’ when their positioning appears imbalanced. An apparent imbalance may signify an as yet incomplete action or event requiring more detailed processing. As such it may refer to phylogenetically ancient stimulus-response mechanisms such as those mediating attentional deployment.

Methodology/Principal Findings

We studied preferences for structural balance or imbalance in week-old domestic chicks (Gallus gallus), using a conditioning procedure to reinforce pecking at either “aligned” (balanced) or “misaligned” (imbalanced) training stimuli. A testing phase with novel balanced and imbalanced stimuli established whether chicks would retain their conditioned behavior or revert to chance responding. Whereas those trained on aligned stimuli were equally likely to choose aligned or misaligned stimuli, chicks trained on misaligned stimuli maintained the trained preference.

Conclusions/Significance

Our results are consistent with the idea that the coding of structural imbalance is primary and even overrides classical conditioning. Generalized to the humans, these results suggest aesthetic judgments based upon structural imbalance may be based on evolutionarily ancient mechanisms, which are shared by different vertebrate species.

Conditioning of transcranial magnetic stimulation: evidence of sensory-induced responding and prepulse inhibition

BACKGROUND

Transcranial magnetic stimulation (TMS) is a non-invasive method for stimulating the human cortex. Classical conditioning is a phenomenon of developed associations between stimuli. Our primary objective was to determine whether TMS effects could be conditioned. Prepulse inhibition represents another relationship between two stimuli, and a secondary assessment was performed to explore this relationship.

METHODS

An auditory-visual conditioning stimulus (CS) was paired with the TMS unconditioned stimulus (US) over motor cortex producing a motor-evoked potential (MEP) unconditioned response (UR). Two versions of the CS-US pairing paradigms were tested, one with a short intertrial interval (ITI) and another with a long ITI. The short ITI paradigm had more CS-US pairings and shorter session duration than the long ITI paradigm. Tests for conditioned responses (CRs) were performed following CS-US pairing (CS+/US+), by presenting the CS alone (CS+/US-). Reverse testing was also performed after CS-US pairing (CS+/US+) in separate sessions, by presenting the US alone (CS-/US+).

RESULTS

Evidence for CRs was found only with the short ITI paradigm. The magnitudes of CRs were smaller than TMS-induced MEPs, and the CRs were found only in a percentage of tests. Prepulse inhibition was robustly evident for the long ITI paradigm, but not for the short ITI paradigm.

CONCLUSIONS

We have found evidence that classical conditioning principles can be applied to brain stimulation in humans. These findings provide a method for exploring brain and behavioral relationships in humans, as well as suggesting approaches to enhance therapeutic uses of TMS or other forms of brain stimulation.

Neural activations of the acquisition of conditioned sexual arousal: effects of contingency awareness and sex

INTRODUCTION

Learning processes like classical conditioning are involved in mediating sexual behavior. Yet, the neural bases underlying these processes have not been investigated so far.

AIM

The aim of this study was to explore neural activations of classical conditioning of sexual arousal with respect to sex differences and contingency awareness.

METHODS

In the acquisition phase, a geometric figure (CS+) was presented for 8 seconds and was followed by highly sexual arousing pictures (UCS), whereas another figure (CS-) predicted neutral pictures. Ratings and contingency awareness were assessed after the entire conditioning procedure. Forty subjects (20 females) were classified into one of four groups according to their sex and the development of contingency awareness (aware females, aware males, unaware females, and unaware males).

MAIN OUTCOME MEASURES

Blood oxygen level dependent (BOLD) responses measured by functional magnetic resonance imaging (fMRI), skin conductance responses (SCRs), and subjective ratings.

RESULTS

fMRI analysis showed two effects (awareness and sex) when comparing CS+ with CS-: (i) aware compared to unaware subjects showed enhanced differentiation (e.g., ventral striatum, orbitofrontal cortex, occipital cortex); and (ii) men showed increased activity compared to women in the amygdala, thalamus, and brainstem. CS+ and CS- ratings differed in aware subjects only. However, no conditioned SCRs occurred in any group.

CONCLUSION

The increased activity in men is in line with theories postulating that men are generally more prone to conditioning of sexual arousal. Further, contingency awareness seems to be an important factor in appetitive learning processes, which facilitates conditioning processes.

The rostral anterior cingulate cortex modulates the efficiency of amygdala-dependent fear learning

BACKGROUND

The rostral anterior cingulate cortex (rACC) and the amygdala consistently emerge from neuroimaging studies as brain regions crucially involved in normal and abnormal fear processing. To date, however, the role of the rACC specifically during the acquisition of auditory fear conditioning still remains unknown. The aim of this study is to investigate a possible top-down control of a specific rACC sub-region over amygdala activation during pavlovian fear acquisition.

METHODS

We performed excitotoxic lesions, temporal inactivation, and activation of a specific sub-region of the rACC that we identified by tracing studies as supporting most of the connectivity with the basolateral amygdala (r(Amy)-ACC). The effects of these manipulations over amygdala function were investigated with a classical tone-shock associative fear conditioning paradigm in the rat.

RESULTS

Excitotoxic lesions and transient inactivation of the r(Amy)-ACC pre-training selectively produced deficits in the acquisition of the tone-shock associative learning (but not context). This effect was specific for the acquisition phase. However, the deficit was found to be transient and could be overcome by overtraining. Conversely, pre-training transient activation of the r(Amy)-ACC facilitated associative learning and increased fear expression.

CONCLUSIONS

Our results suggest that a subregion of the rACC is key to gating the efficiency of amygdala-dependent auditory fear conditioning learning. Because r(Amy)-ACC inputs were confirmed to be glutamatergic, we propose that recruitment of this brain area might modulate overall basolateral amygdala excitatory tone during conditioned stimulus-unconditioned stimulus concomitant processing. In the light of clinical research, our results provide new insight on the effect of inappropriate rACC recruitment during emotional events.