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How does the brain tell time?
The neural basis of timing in the range of tens to hundreds of milliseconds is the range is critical for simple interval and duration discrimination, speech and music recognition, and motor coordination. Temporal processing in this range is a generalized property of cortical networks, and does not rely on specialized or centralized mechanisms. Timing is more akin to the dynamics of ripples on a pond than a clock. Our representation of time is inherently nonlinear, and subject to a number of illusions and distortions.
Clocking the Brain’s Memory Making Circuits
Theta oscillations are a clocking signal that strongly modulates activity in the hippocampus, a brain area critical for the formation of long-term memories. The prevailing view has been that theta oscillations are synchronized throughout the hippocampus. Experiments have shown that theta oscillations are in fact traveling waves that pattern hippocampal activity not only in time, but also across anatomical space. Hence time in the hippocampus, as clocked by theta oscillations, is organized in a way similar to time on Earth—in a regular progression of local time zones.
Building memories across temporal gaps
Our memories enable us to vividly re-experience past events, feelings and thoughts. Importantly, many of the original experiences consist of multiple event details and unfold over extended time periods that exceed the temporal constraints for synaptic learning (i.e., long-term potentiation [LTP]). How do our brains overcome those gaps in order to make discontiguous experiences amenable to LTP and thereby convert them into a unified memory trace? Our recent work has focused on revealing the building blocks of our memories and the neural mechanisms through which they are assembled in the brain. We found that specific regions in the medial temporal lobe (MTL) play a key role for intact memory and that there exists a clear division of labor in the service of successful memory formation. In particular, our data suggest that the human hippocampus is critical for integrating separate event details across space and time and thus provides the 'glue' with which our vivid memory traces are formed.
The transparent mind: Reading thoughts from human brain activity.
Recent advances in human neuroimaging have shown that it is possible to accurately read out a person's conscious experience based only on non-invasive fMRI measurements of their brain activity. This "brain reading" is possible because each thought is associated with a unique pattern of brain activity that can serve as a "fingerprint" of this thought in the brain. By training a computer to recognize these fMRI "thought patterns" it is possible to read out what someone is currently thinking with high accuracy. This talk will give an overview of this emerging field and will show how brain science can read out a person's visual imagery, their emotions and their future plans. For example, it is possible to read out a person's concealed intentions and even to predict how they are going to decide a few seconds later. Finally, the talk will discuss fundamental challenges and limitations of the field, along with the ethical question if such methods might one day
be a danger to our mental privacy.
Studying time in the Neurosciences: The conceptual framework.
The concept of time, like the somewhat related concept of space, has been at center stage in human thought since ancient times. About one hundred years ago physics taught us to see the two as related sides of one entity and the whole as not absolute and universal but rather relative and context-dependent. I will present an overview of the use of the concepts of time and space, starting from their ancient Greek roots and extending via the thoughts of Newton, Kant, and others to present day theories. In this, special attention will be paid to the overlap, the differences, as well as the frequently observed tension between concept-using empirical sciences, especially neurosciences, and concept-reflecting, i.e. philosophical ways of seeing these matters. Here, the synthesis aims to show not only that, but also how these two ways of seeing complement each other and that their constructive co-operation can be most fruitful for both domains.
Reuben Heyday Margolin
We see waves everywhere: in water, in wind, in the contours of a flame. I have spent the last ten years making kinetic sculptures inspired by these movements. Seeking to combine the logic of mathematics with the sensuousness of nature, I've built a series of mechanical mobiles that have been exhibited both in science and art museums. I'll show photos and video of completed wave sculptures, as well as a couple short documentaries about making these kinetic and mathematical artworks.
Making sense of time: The embodied nature of human abstraction
Events that already occurred and events that have not occurred yet, cannot be perceived directly thought the senses. In order to grasp them, refer to them, talk about them, and make sense of them, we must construe them in a stable and tractable manner via the recruitment of bodily-grounded mechanisms that make human imagination possible. Thus, humans from all over the world, speaking different languages, naturally express (and apparently, think about) everyday temporal events as if they were spatial entities. This remarkable but ubiquitous phenomenon manifests itself via ordinary linguistic metaphorical expressions such as (a) "we are approaching the end of the semester," and (b) "Easter is approaching." Moreover, beyond words and grammar, this phenomenon can be observed also through largely unconscious motor actions co-produced with speech-- spontaneous gestures, which reveal its deep conceptual nature. In this presentation I will try to give an overview of how the question of human conceptualization of time can be studied empirically using a variety of research methods, from ethnographic fieldwork to psycholinguistic experiments to neuroimaging. Research in cognitive linguistics and in processing of temporal metaphors has traditionally distinguished between Moving-Ego conceptual metaphors, as in (a) above, and Moving-Time ones, as in (b). Both of these conceptual metaphors involve time events in reference to an Ego, which specifies the present time “Now” where Future is in front of ego and Past is behind ego. I will argue, however, that the picture is more complicated than that: (1) not all spatial construal of time have the Ego as reference point (Ego-RP), and (2) the specified bodily orientation is not universal. I will provide evidence from a priming psycholinguistic experiment to support (1), which shows that there is a fundamental (perhaps more primitive) spatial metaphorical construal of time defined after Time events—not Ego—as reference points (Time RP mapping). Regarding (2) I will show convergent empirical evidence (lexical-metaphorical-gestural) from my fieldwork in the South American Andes, which shows that the Aymara people operate with an unusual Past-In-Front-Of-Ego and Future-Behind-Ego mapping. Moreover, from a recent fieldwork investigating time construal in the Yupno culture from the remote mountains of Papua New Guinea, I'll show some preliminary data we have that suggests that some human groups can also naturally conceive time in terms of an entire different set of spatial frames of reference, namely, geocentric (not ego-centric) ones. Finally, regarding Ego-RP mappings, I will present some of our preliminary neuroimaging (fMRI) studies that address the question of the neural basis of the Ego-RP space-time mapping, especially what concerns the role of the ventral-intra parietal area (VIP) and the poly-sensory Zone (PZ) of the human brain. Implications for “Embodiment” and bodily-grounded approaches to the understanding of human imagination and abstraction will be discussed.
Time, Change, and the Structure of Immediate Experience
‘I saw the ball cross the line’, ‘I watched her stand still, motionless, for several seconds’, ‘I can hear the bell ringing’: claims such as these are a familiar part of everyday life. So clearly, if our ordinary ways of talking are anything to go by, both change and persistence feature in our immediate experience. But what underlies these ordinary ways of talking? Are we really capable of directly apprehending phenomena which possess temporal extension? Among philosophers interested in such matters, there has long been a marked divergence of opinion. Some hold that our talk of perceiving change (or persistence) is just that: talk, and nothing more. Those who adopt this line claim that change cannot feature in our immediate experience, on the grounds that change takes time, our consciousness is confined to the present, and the present is durationless. Others maintain that this view is wrong, and that we do directly experience change. However, in this camp there are very different views regarding how this is possible. Some philosophers, reluctant to give up the idea that experience is confined to the momentary present, have developed accounts of the structure of consciousness according to which our immediate experience of change occurs in episodes of experiencing that themselves lack duration. Philosophers in the second main camp maintain that there is no need to adopt such counterintuitive contortions. What we must do instead is reject the dogma that consciousness cannot extend beyond the present. If we take this step – if we allow that our direct awareness can extend a little way through time – there is no difficulty whatsoever in understanding how we are able to directly experience change and persistence. After taking a general look at the considerations which have led philosophers to adopt these very different positions, I will take a more detailed look at the two main ways of incorporating change and persistence into our immediate experience, focusing on the problems which confront these very different conceptions of the temporal structure of consciousness. After arguing that, on balance, the approach which allows our awareness to extend a brief way through time is superior to the alternatives, I will take a brief look at some objections to this approach which have appeared in the recent literature, and suggest some ways in which these objections can be countered.