Non-invasive brain stimulation (NIBS) is a method for the study of cognitive function that is quickly gaining popularity. It bypasses the correlative approaches of other imaging techniques, making it possible to establish a causal relationship between cognitive processes and the functioning of specific brain areas. Like lesion studies, NIBS can provide information about where a particular process occurs. However, NIBS offers the opportunity to study brain mechanisms beyond process localisation, providing information about when activity in a given brain region is involved in a cognitive process, and even how it is involved. When using NIBS to explore cognitive processes, it is important to understand not only how NIBS functions but also the functioning of the neural structures themselves. We know that NIBS techniques have the potential to transiently influence behaviour by altering neuronal activity, which may have facilitatory or inhibitory behavioural effects, and these alterations can be used to understand how the brain works. Given that NIBS necessarily involves the relatively indiscriminate activation of large numbers of neurons, its impact on a neural system can be easily understood as modulation of neural activity that changes the relation between noise and signal. In this review, we describe the mutual interactions between NIBS and brain activity and provide an updated and precise perspective on the theoretical frameworks of NIBS and their impact on cognitive neuroscience. By transitioning our discussion from one aspect (NIBS) to the other (cognition), we aim to provide insights to guide future research.

This paper reviews evidence and theories concerning the nature of stimulus representations in Pavlovian conditioning. It focuses on the elemental approach developed in Stimulus Sampling Theory (Atkinson & Estes, 1963;Bush & Mosteller, 1951b) and extended by McLaren and Mackintosh (2000;2002), and contrasts this with models that that invoke notions of configural representations that uniquely code for different patterns of stimulus inputs (e.g., Pearce, 1987Pearce, , 1994Wagner & Brandon, 2001). The paper then presents a new elemental model that emphasizes interactions between stimulus elements. This model is shown to explain a range of behavioral findings, including those (e.g., negative patterning and biconditional discriminations) traditionally thought beyond the explanatory capabilities of elemental models. Moreover, the model offers a ready explanation for recent findings reported by Rescorla (2000;2001;2002b) concerning the way that stimuli with different conditioning histories acquire associative strength when conditioned in compound.

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Four experiments studied contextual control over rats' freezing to conditioned stimuli (CSs) that had been paired with shock and were then extinguished. In Experiment 1, rats were exposed to a CS A-shock and a CS B-shock pairing in Context C. CS A was then extinguished in Context A, and CS B in Context B. Freezing was renewed when each CS was presented in the context where the other CS had been extinguished. In Experiments 2-4, rats were exposed to a CS A-shock pairing in A and a CS B-shock pairing in B. They were then exposed to Context C where one, both, or neither of the CSs were extinguished, or where both CSs continued to be reinforced. On test, the rats froze more to CS A than to CS B in Context A, and more to CS B than to CS A in Context B, but only if the CSs had been extinguished. Thus, after extinction, rats use contexts to regulate retrieval not only of their memory for extinction, but also of their memory for the original conditioning episode.

Six experiments used rats to study the effects of the beta-carboline FG 7142 on extinction of fear responses (freezing) to an auditory cue that had signalled footshock. Subcutaneous injection of FG 7142 interfered with the development of extinction without having any detectable effect on the rats' levels of fear prior to extinction. Injection of FG 7142 also reversed extinction, partially reinstating fear responses that had been extinguished previously. A similar reinstatement of extinguished fear was seen when rats were tested for fear of the cue in a different chamber. The reinstatement produced by FG 7142 and that caused by context shift were not additive: FG 7142 did not increase extinguished fear if rats were tested in the different chamber. Finally, FG 7142 had no detectable effect on the latent inhibition of fear produced by repeatedly presenting the cue alone before conditioning with shock, even though this inhibition, like extinction, was affected by a shift in context. The present findings indicate that GABA transmission at GABA(A) receptors is involved in the inhibition of extinguished fear, and that this effect of GABA is regulated by those cues that constitute the extinction context.

Rats exposed to a simultaneous compound of a flavor and sucrose subsequently exhibited a preference for the flavor over water. This preference persisted across repeated testing even though the flavor was presented in the absence of sucrose. The preference did, however, extinguish if the rats were hungry when trained or tested, or if they had been reexposed to sucrose between training and test. Though failing to extinguish the preference, presentation of the flavor outside the compound protected it from the effects of sucrose devaluation, indicating that these presentations extinguished the within-compound association between the flavor and sucrose. The authors conclude that the hedonic reaction elicited by sucrose imbues the flavor with the same hedonic properties, and these properties maintain the preference independently of the flavor-sucrose association.

The authors studied the role of context in reinstatement. Freezing was reinstated when the conditioned stimulus (CS) was extinguished in 1 context and rats moved to another context for reexposure to the shock unconditioned stimulus (US) and test. It was also reinstated (rather than renewed) when rats were shocked in the extinction context and moved to another context for test. This reinstatement was CS specific and reduced by nonreinforced exposures to the extinction context. Rats shocked in the context in which a stimulus had been preexposed froze when tested in another context. These findings suggest 2 roles for context in reinstatement: conditioning of the test context (M. E. Bouton, 1993) and mediated conditioning by the extinction context (P. C. Holland, 1990).

33 The mammalian visual system, from retina to neocortex, has been extensively studied at both 34 anatomical and functional levels. Anatomy indicates the cortico-thalamic system is hierarchical, 35 but characterization of cellular-level functional interactions across multiple levels of this 36 hierarchy is lacking, partially due to the challenge of simultaneously recording activity across 37 numerous regions. Here, we describe a large, open dataset (part of the Allen Brain Observatory) 38 that surveys spiking from units in six cortical and two thalamic regions responding to a battery of 39 visual stimuli. Using spike cross-correlation analysis, we find that inter-area functional 40 connectivity mirrors the anatomical hierarchy from the Allen Mouse Brain Connectivity Atlas. 41Classical functional measures of hierarchy, including visual response latency, receptive field 42 size, phase-locking to a drifting grating stimulus, and autocorrelation timescale are all correlated 43 with the anatomical hierarchy. Moreover, recordings during a visual task support the behavioral 44 relevance of hierarchical processing. Overall, this dataset and the hierarchy we describe provide 45 a foundation for understanding coding and dynamics in the mouse cortico-thalamic visual 46 system. 47