Clahsen has presented an impressive range of psycholinguistic data from German regular and irregular inflection to support the view that lexical memory and the combinatorial operations of grammar are subserved by distinct mental mechanisms. Most of the data are convincing and important. I particularly applaud Clahsen's effort to extend this lexical/grammatical dichotomy from mind to brain. Here I discuss some problems with the evidence presented by Clahsen in support of a neural lexical/grammatical dichotomy, and offer some additional evidence to reinforce this neural distinction.

Aggleton & Brown argue that a hippocampal-anterior thalamic system supports the “recollection” of contextual information about previous events, and that a separate perirhinal-medial dorsal thalamic system supports detection of stimulus “familiarity.” Although there is a growing body of human literature that is in agreement with these claims, when recollection and familiarity have been examined in amnesics using the process dissociation or the remember/know procedures, the results do not seem to provide consistent support. We reexamine these studies and describe the results of an additional experiment using a receiver operating characteristic (ROC) technique. The results of the reanalysis and the ROC experiment are consistent with Aggleton & Brown's proposal. Patients with damage to both regions exhibit severe deficits in recollection and smaller, but consistent, deficits in familiarity.

The theory of consciousness proposed by O'Brien & Opie is open to the Sorites paradox, for it defines a consciousness system internally in terms of computationally relevant units which add up to consciousness only if sufficient in number. The Sorites effect applies on the assumed level of features.

Gold & Stoljar are right in their thesis but incomplete in not pointing out that there are many other arguments from cognate sciences suggesting that a radical eliminativist neuroreductionism is unlikely to be achieved. The radical neuron doctrine they criticize is only a hoped for dogma that cannot be verified, whereas a constrained monistic materialism (with only partial reductionism) is subject to immediate test by applying such criteria as combinatorial complexity and thermodynamic irreversibility.

Colours are not the sorts of thing that are amendable to traditional forms of scientific explanation. To think otherwise is to mistake their ontology and ignore their normativity. The acquisition and use of colour categories is constrained by the logic of colour grammars.

The proposal that the hippocampus is important for the encoding of episodic information, but not familiarity-based recognition, is incompatible with the available data. An alternative way to think about functional specialization within the medial temporal lobe memory system is suggested, based on neuroanatomy.

Clahsen's theory raises problems that make it seem untenable. As an alternative, a constructivist neural network model is reported that develops a modular architecture and in which a single associative mechanism produces all inflections, displaying an emergent dissociation between regular and irregular verbs. Thus, Clahsen's rejection of associative models of inflection concerns only a subgroup of these models.

This commentary concentrates on the nature of irregularity in morphology. What is called “irregular” in the target article by Clahsen is not a homogeneous class. Rather, there are areas of strong subregularities in the domains both of German participle formation and of German plural information that need to be distinguished from the irregular domain.

The goal of our target article was to review a number of emerging facts about the effects of limbic damage on memory in humans and animals, and about divisions within recognition memory in humans. We then argued that this information can be synthesized to produce a new view of the substrates of episodic memory. The key pathway in this system is from the hippocampus to the anterior thalamic nuclei. There seems to be a general agreement that the importance of this pathway has previously been underestimated and that it warrants further study. At the same time, a number of key questions remain. These concern the relationship of this system to another temporal-lobe/diencephalic system that contributes to recognition, and the relationship of these systems to prefrontal cortex activity.

The complexity of modern neurobiology in even a comparatively restricted area such as use-dependent synaptic plasticity is underestimated by the authors. This leads them to reject a neurobiological model of learning as conceptually parasitic on the psychology of conditioning, on the basis of objections that are shown to be unsustainable. An argument is also advanced that neurobiologists hold an intermediate version of the neuron doctrine rather than a conflated one. In this version, neurobiologists believe that psychology will eventually be underpinned by neurobiology but are agnostic about the extent of upheaval that this will produce in psychology.

O'Brien & Opie's position is consistent with the existence of implicit learning and subliminal perception below a subjective threshold but it is inconsistent with various other findings in the literature. The main problem with the theory is that it attributes consciousness to too many things. Incorporating the higher order thought theory renders their position more plausible.

Colour word usage within languages follows the same ordering as that proposed by Berlin and Kay between languages. This provides additional validation and support for Berlin and Kay's schema.

German noun plurals not ending in -s are not as irregular as Clahsen suggests. Feminine nouns get the -n plural, unless they umlaut and are subject to a constraint that requires a reduced final syllable in the plural. Another regular class is masculine nouns ending in schwa, which are weakly inflected. It is suggested that more differentiated psycholinguistic experiments can identify these regularities.

O'Brien & Opie present an attractive alternative to the popular but flawed computational process approach to conscious awareness. Their “vehicle” theory, however, is itself seriously flawed by overstrict allegiance to the notion that explicit representation and stability are defining hallmarks of consciously experienced neural activity patterns. Including reentrant interactions among time-varying patterns in different brain areas can begin to repair their theory.

Saunders and van Brakel's observation that “linguistic evidence provides no grounds for the universality of basic color categories” also applies to the concept of “colour” itself. The language of “seeing” is rooted in human experience, and its basic frame of reference is provided by the universal rhythm of “light” days and “dark” nights and by the fundamental and visually salient features of human environment: the sky, the sun, vegetation, fire, the sea, the naked earth.

When circumscribed brain regions are damaged in humans, highly specific impairments in language, memory, problem solving, and cognition are observed. Neurosurgery such as “split brain” or hemispherectomy, for example, has shown that encompassing regions, the left and right cerebral hemispheres, each control human behavior in unique ways. Observations stretching over 100 years of patients with unilateral focal brain damage have revealed, without the theoretical benefits of “cognitive neuroscience” or “cognitive psychology,” that human behavior is indeed controlled by the brain and its neurons.

Extraversion has two central characteristics: (1) interpersonal engagement, which consists of affiliation (enjoying and valuing close interpersonal bonds, being warm and affectionate) and agency (being socially dominant, enjoying leadership roles, being assertive, being exhibitionistic, and having a sense of potency in accomplishing goals) and (2) impulsivity, which emerges from the interaction of extraversion and a second, independent trait (constraint). Agency is a more general motivational disposition that includes dominance, ambition, mastery, efficacy, and achievement. Positive affect (a combination of positive feelings and motivation) is closely associated with extraversion. Extraversion is accordingly based on positive incentive motivation.

Parallels between extraversion (particularly its agency component) and a mammalian behavioral approach system based on positive incentive motivation implicate a neuroanatomical network and modulatory neurotransmitters in the processing of incentive motivation. A corticolimbic-striatal-thalamic network (1) integrates the salient incentive context in the medial orbital cortex, amygdala, and hippocampus; (2) encodes the intensity of incentive stimuli in a motive circuit composed of the nucleus accumbens, ventral pallidum, and ventral tegmental area dopamine projection system; and (3) creates an incentive motivational state that can be transmitted to the motor system.

Individual differences in the functioning of this network arise from functional variation in the ventral tegmental area dopamine projections, which are directly involved in coding the intensity of incentive motivation. The animal evidence suggests that there are three neurodevelopmental sources of individual differences in dopamine: genetic, “experience-expectant,” and “experience-dependent.” Individual differences in dopamine promote variation in the heterosynaptic plasticity that enhances the connection between incentive context and incentive motivation and behavior.

Our psychobiological threshold model explains the effects of individual differences in dopamine transmission on behavior, and their relation to personality traits is discussed.

We propose that a control system will address the causal dynamics of the neural network that Depue & Collins regard as underlying extraversion. We briefly describe a control system approach and articulate the notion of integration. The integration of goals and regards is achieved by subcortical assessment of reward in the nucleus accumbens and VTA (ventral tegmental area) transmission of this information largely by dopaminergic systems and representation of reward in the MOC (medial orbital cortex). Thus reward information is collected, integrated, and evaluated in the MOC. Such control decisions rely on constraining processes, a functional property of the MOC mediated largely by serotonergic neurons.

To assess O'Brien & Opie's connectionist vehicle theory of consciousness, (1) it is not enough to point to the methodological weakness of certain experiments (dichotic listening, etc.). Successful cognitive theories postulating explicit unconscious representations have to be taken into account as well. (2) The distinction between vehicle and process theories cannot be drawn in the way envisaged by the authors because a representation's explicitness depends not only on its structural but also on its processing properties. (3) The stability of an activation vector is not very suitable for implementing the explicitness of a representation.

Dual-mechanism models of language maintain a distinction between a lexicon and a computational system of linguistic rules. In his target article, Clahsen provides support for such a distinction, presenting evidence from German inflections. He argues for a structured lexicon, going beyond the strict lexicon versus rules dichotomy. We agree with the author in assuming a dual mechanism; however, we argue that a next step must be taken, going beyond the notion of the computational system as specific rules applying to a linguistic domain. By assuming a richer lexicon, the computational system can be conceived as a more general binding process that applies to different linguistic levels: syntax, morphology, reading, and spelling.