Merker makes a strong case for the upper brain stem as being the neural home of primary or phenomenal consciousness. Though less emphasized, he makes an equally strong and empirically supported argument for the critical role of the mesodiencephalon in basic emotion processes. His evidence and argument on the functions of brainstem systems in primary consciousness and basic emotion processes present a strong challenge to prevailing assumptions about the primacy of cognition in emotion-cognition-behavior relations.

I argue that the partial-report results Block cites do not establish that phenomenology overflows cognitive accessibility, as Block maintains. So, without additional argument, the mesh he sees between psychology and neuroscience is unsupported. I argue further that there is reason to hold, contra Block, that phenomenology does always involve some cognitive access to the relevant experience.

A number of difficulties encumber the Suddendorf & Corballis (S&C) proposal regarding mental time travel into the future. Among these are conceptual issues turning on the inherent asymmetry of time and causality with regard to past and future, and the bearing of such asymmetry on the uses and utility of retrospective versus prospective mental time travel, on which I comment.

Suddendorf & Corballis (S&C) claim that mental time travel has significantly affected human cultural change. This echoes a common criticism of theories of Darwinian cultural evolution: that, whereas evolution is blind, culture is directed by people who can foresee and plan for future events. Here I argue that such a claim is premature, and more rigorous tests of S&C's claim are needed.

Consistent with the target article, recent evidence indicates that the superior colliculus (SC) is somehow involved in target selection. However, it is not yet known whether this function is inherent to the SC or inherited from its inputs, how the selection process occurs for different movements, or how target selection by the SC is related to covert selection (i.e., attention).

Block proposes that phenomenal experience overflows conscious access. In contrast, we propose that conscious access overflows overt report. We argue that a theory of phenomenal experience cannot discard subjective report and that Block's examples of phenomenal “overflow” relate to two different types of perception. We propose that conscious access is more than simply readout of a pre-existing phenomenal experience.

Our aim in this reply is to defend Global Workspace theory (GWT) from the challenge of Block's article. We argue that Block's article relies on an outdated and imprecise concept of access, and perpetuates a common misunderstanding of GWT that conflates the global workspace with working memory. In the light of the relevant clarifications, Block's conclusion turns out to be unwarranted, and the basic tenets of GWT emerge unscathed.

Mental time travel requires the sense of a past and future self, which is lacking in the early years of life. Research on the development of autobiographical memory and development of self sheds light on the difference between memory in other animals and its cultural narrative basis in humans.

Merker's definition of consciousness excludes self-reflective thought, making his proposal for decorticate consciousness not particularly ground-breaking. He suggests that brainstem sites are neglected in current theories of consciousness. This is so because broader definitions of consciousness are used. Split-brain data show that the cortex is important for full-blown consciousness; also, behaviors exhibited by hydranencephaly patients and decorticated rats do not seem to require reflective consciousness.

The number of studies concerning the neurobiology of human prospection is now rapidly exploding. Recent works suggest that prospection can be better understood in a broader context of self-projection into other times, places, or agents that can share the same cerebral basis involving medial aspects of prefrontal, parietal, and temporal cortices. Mental time travel may be extended more generally to “mental traveling,” accomplished by stimulus-independent mental processes typical of human thought.

Can phenomenality without access occur? We suggest that the crucial issue is not to show phenomenality that cannot be accessed, but whether phenomenality sometimes simply is not accessed. Considering this question leads to positing a distinct, second form of consciousness: Reflective consciousness. The most important form of access is then from phenomenal (first-order) to reflective (second-order) consciousness.

To further illuminate the nature of conscious states, it may be progressive to integrate Merker's important contribution with what is known regarding (a) the temporal relation between conscious states and activation of the mesodiencephalic system; (b) the nature of the information (e.g., perceptual vs. premotor) involved in conscious integration; and (c) the neural correlates of olfactory consciousness.

Merker argues that subcortical regions are sufficient for the constitution of consciousness as “immediate, unreflective experience” as distinguished from self-consciousness. My point here is that Merker neglects the differentiation between pre-reflective self-awareness and reflective self-consciousness. Pre-reflective self-awareness allows us to immediately and unreflectively experience our self, which functionally may be mediated by what I call self-related processing in subcortical regions.

Block's argument against correlationism depends in part on a view about what subjects in certain experiments can be aware of phenomenally. Block's main source of evidence for this view is introspection. I argue that introspection should not be trusted in this respect. This weakens Block's argument and undermines correlationism at the same time.

We are not entirely satisfied with the evolutionary explanation provided by Suddendorf & Corballis (S&C) for why only humans should be capable of advanced mental time travel. General social factors do not suffice, given that other primates are also highly social. We discuss the evolutionary mechanisms that have generated mental time travel typical to humans, focusing on ecological factors.

Disregard of primary-process consciousness is endemic in mind science. Most neuroscientists subscribe to ruthless reductionism whereby mental qualities are discarded in preference for neuronal functions. Such ideas often lead to envisioning other animals, and all too often other humans, as unfeeling zombies. Merker correctly highlights how the roots of consciousness exist in ancient neural territories we share, remarkably homologously, with all the other vertebrates.

Although the mental time travel (MTT) hypothesis provides a rich, conceptual framework, the absence of clear, empirically tractable, behavioural criteria for determining the capacity for MTT restricts its usefulness in comparative research. Examples of empirical criteria for evaluating MTT in animals are given. We also question the authors' evaluation of semantic foresight and their even-handedness in assessing human and nonhuman behaviour.

Block tries to show that the results of the Sperling experiment lend support to the view that phenomenology outstrips cognitive accessibility. I argue that Block fails to make a compelling case for this general claim on the basis of the Sperling data.

If the phenomenality of consciousness admits of degrees and can be partial and indeterminate, then Block's inference to the best explanation may need to be revaluated both in terms of the supposed data on phenomenal overflow and the range of alternatives against which his view is compared.

We consider the relation between past and future events from the perspective of the constructive episodic simulation hypothesis, which holds that episodic simulation of future events requires a memory system that allows the flexible recombination of details from past events into novel scenarios. We discuss recent neuroimaging and behavioral evidence that support this hypothesis in relation to the theater production metaphor.