We recently found orientation constancy with respect to direction of gravity in the alert monkey. This seems to rely on a polysensory interaction that involves different sense-specific reference frames. Thus, we will challenge the assumption that the sense-specific reference frames are mutually exclusive. At the same time, we will highlight the dynamic tuning of the receptors that might rely on cross-modal mechanisms.

According to a “presence/absence hypothesis,” the hippocampus is not necessary for the formation of learned associations between currently present stimuli and responses (as in classical conditioning), but is necessary whenever a stimulus, if it is to activate a particular response, must first activate a memory-representation of something not present in the here-and-now. The distinction between responses made to present stimuli as opposed to (memories of) absent stimuli was first stressed by Romanes (1889), but we find evidence in the target article that supports the relevance of this distinction to our understanding of hippocampal functioning.

Findlay & Walker's target article proposes a model of saccade generation related to the underlying neuroscience. A problem with such models is the number of brain areas showing oculomotor function. Traditionally, therefore, models have been partial, usually concentrating either on cortex (Liu et al. 1997; Pierrot Deseilligny et al. 1995) or on the superior colliculus and brainstem circuits (Moschovakis 1994; Van Gisbergen et al. 1993). Findlay & Walker's model attempts to integrate both levels within a functional framework. To some extent it falls between two stools. For example, some functions that the authors ascribe to subcortical regions may actually occur at the cortical level.

True, there may be two language-processing systems, lexicon and syntax. However, could we not say more than that they are computationally and linguistically distinct? Where are they in the brain, why are they where they are, and how can their distinctness and functional properties be explained by biological principles? A brain model of language is necessary to answer these questions. One view is that two different types of corticocortical connections are most important for storing rules and their exceptions: short-range connections within the perisylvian language cortex and long-range connections between this region and other areas. Probabilities of neuroanatomical connections plus associative learning principles explain why different connection bundles specialize in rule storage versus exception learning. Linguistic issues related to language change and plural formation in German are addressed in closing.

Gold & Stoljar pose a dilemma for linguistics should neurobiology win out as the science of mind. The dilemma can be avoided by reestablishing linguistics as an autonomous discipline, rather than a branch of the science of mind. Independent considerations for doing this are presented.

For a theory of phenomenal consciousness, the real issue is not that between vehicle and process, but between naturalistic and deconstructive theories. Most current naturalistic theories combine a hypothesis about the neural correlate of consciousness with a subsequent naturalistic proposal about how to close the explanatory gap. Deconstructive theories use theses about the neural correlate of consciousness only to motivate and support their claim that the “hard problem” of consciousness is a pseudo-problem which is not to be solved, but rather dissolved on non-naturalistic grounds. O'Brien & Opie present a hypothesis concerning the neural correlate of consciousness, but no genuine strategy to close the explanatory gap. Their theory can, however, contribute to the success of a deconstructive theory of PC.

Clahsen's compelling evidence for the dual-mechanism model of the lexicon derives in part from the use of cross-linguistic data in psycholinguistic research. This approach reflects a growing (and positive) trend toward incorporating data from several languages when analyzing and modeling human language behavior. This perspective should be expanded to include data from typologically distinct languages to develop more explanatory models of language.

In line with my model of object motion perception (Wertheim 1994) and in contradistinction to what Stoffregen (1994) states, Sauvan's data suggest that percepts of motion are not sense specific. It is here argued that percepts of object- or self-motion are neither sense specific nor do they necessarily stem from what Stoffregen calls “kinematic events.” Stoffregen's error is in believing that we can only perceive object- or self-motion relative to other objects, which implies a failure to realise that percepts of absolute object- or self-motion in space (relative to the earth's surface) do exist as well, even when the earth's surface itself is not perceived.

Gold & Stoljar's argument rejecting the “explanatory sufficiency” of the radical neuron doctrine depends on distinguishing it from the trivial neuron doctrine. This distinction depends on the thesis of “supervenience,” which depends on Hume's regularity theory of causation. In contrast, the radical neuron doctrine depends on a physical theory of causation, which denies the supervenience thesis. Insofar as the target article argues by drawing implications from the premise of Humean causation, whereas the radical doctrine depends on the competing premise of physical causation, the resulting critique of the neuron doctrine amounts largely to begging the question of causation.

O'Brien & Opie's vehicle hypothesis is an attractive framework for the study of consciousness. To fully embrace the hypothesis, however, two of the authors' claims should be extended: first, since phenomenal content is entirely dependent on occurrent brain events and only contingently correlated with external events, it is no longer necessary to regard states of consciousness as representations. Second, the authors' insistence that only stable states of a neural network are conscious seems ad hoc.

The concept of a salience map has become important for the development of theories of visual attention and saccade generation. Recent studies have shown that the frontal eye fields have all of the characteristics of a salience map.

Aggleton & Brown rightly point out the shortcomings of the medial temporal lobe hypothesis as an approach to anterograde amnesia. Their broader perspective is a necessary corrective, and one hopes it will be taken very seriously. Although they correctly note the dangers of conflating recognition and recall, they themselves make a similar mistake in discussing familiarity; we suggest an alternative approach. We also discuss implications of their view for an analysis of retrograde amnesia. The notion that there are two routes by which the hippocampus can reactivate neuronal ensembles in the neocortex could help us understand some currently puzzling facts about the dynamics of memory consolidation.

Three comments are made. The proposal that recollection and familiarity-based recognition take different thalamic routes does not fit recent experimental evidence, suggesting that mediodorsal thalamus acts in an integrative role with respect to prefrontal cortex. Second, the role of frontal cortex in episodic memory has been understated. Third, the role of the hippocampal axis is likely to be the computation and storage of ideothetic information.

Clahsen's claim to contribute arguments for dual mechanisms based on rule analysis and against connectionist proposals is refuted. Both types of modeling are inadequate for principled reasons.

O'Brien & Opie's connectionist interpretation of “vehicle,” “process,” and “explicit representation” depends heavily on the notions of “information” and “information processing” that underlie the classic account. When the “cognitivist” assumptions, shared by both accounts, are removed, the connectionist versus classic contrast appears to be between behavioral and linguistic accounts.

Gold & Stoljar's target article is important because it shows the limitations of neurobiological theories of the mind more powerfully than previous philosophical criticisms, especially those that focus on the subjective nature of experience and those that use considerations from philosophy of language to argue for the holism of the mental. They use less controversial assumptions and clearer arguments, the conclusions of which are applicable to the whole of neuroscience. Their conclusions can be applied to psychiatry to argue that, contrary to many researchers' assumptions, the approaches to both understanding and treating mental disorders must be interdisciplinary.

The functional schema in the Findlay & Walker target article presents an understanding of oculomotor behavior primarily at an algorithmic level of analysis. Although such an analysis is an important first step, present knowledge of the neuroscientific substrate for oculomotor behavior is sufficiently advanced to support, if not warrant, computationally explicit models explaining how oculomotor behavior is implemented by this substrate. The literature contains a growing number of examples of this strategy, which we illustrate using our work.

O'Brien & Opie's (O&O's) theory demands a view of unconscious processing that is incompatible with virtually all current PDP models of neural activity. Relative to the alternatives, the theory is closer to an AI than a parallel distributed processing (PDP) perspective, and its treatment of phenomenology is ad hoc. It raises at least one important question: Could features of network relaxation be the “switch” that turns an unconscious into a conscious network?

Aggleton & Brown suggest that whereas familiarity is computed in perirhinal cortex, the hippocampus contributes to recollection. This account raises issues about the definition of amnesia, clarifies confusion about dual-process models of recognition, and sits comfortably with accounts of hippocampal function from outside the amnesia literature. The model can – and should – be tested. Some preliminary data suggest that it may need changes.

This commentary is intended to illuminate Gold's & Stoljar's main contentions by exploiting a favorite comparison, namely, that between biology and electronics. Roughly, and leaving out Darwinian theory and the like, biology is physics and chemistry plus natural history just as electronics is physics plus wiring diagrams. Natural history (even that discovered by sophisticated apparatus such as electron microscopes) contains generalizations, not laws. Psychology and cognitive science typically give more abstract explanations, as do “block diagrams” in electronics, and are less dispensable.