I just visited the ESI SyNC 2024 conference on the topic of "Time in the brain". There, I interviewed Hugo Merchant, an electrophysiologist at UNAM in Juriquilla, Mexico. Hugo works with macaques, who can rhythmically tap their fingers synchronized to a visual or auditory beat. By studying macaque neural activity in dimensionality-reduced spaces, he wants to understand how the brain encodes different time intervals. For an overview of our conversation, see the timestamps below.

Timestamps:

(00:00:00) - Intro

(00:02:57) - Monkeys rhythmic finger tapping

(00:08:27) - Timing network in pre-motor cortex and basal ganglia

(00:12:43) - Circular neural trajectories

(00:16:08) - Mapping latent space to single-cell physiology

(00:20:15) - Experimentally slowing the clock

(00:23:19) - Spatial organization of circuits

(00:27:59) - Error correction & single-trial analyses

(00:38:57) - Bayesian & SNN models

Uri Hasson runs a lab in Princeton, where he investigates the underlying neural basis of natural language acquisition and processing as it unfolds in the real world. As Uri visited Tübingen (where I am doing my master's), we were able to meet in person. Originally, I planned to talk about his idea of temporal receptive windows, and how different brain regions (e.g. default mode network) operate at different timescales. However, we ended up talking more about Wittgenstein, evolution, and ChatGPT. An underlying thread throughout the conversation was that (for both biological and artificial agents), language is not clever symbol and rule manipulation but a brute force fitting to statistics across (Wittgensteinian) 'contexts'. This view is best articulated in Uri's Direct Fit paper. We also connect this to transformers and discuss what's missing in AI. The answer here is multimodal integration, episodic memory, and interactive sociality). At the end, I ask Uri about his 1000 days project, talking to crows, and "understanding" in neuroscience/AI.

Timestamps:

(00:00:00) - Intro

(00:04:52) - Studying language in the real world

(00:07:57) - Wittgenstein

(00:11:10) - Evolution and the default mode network

(00:20:54) - Overparameterized deep learning works

(00:25:02) - Direct Fit paper and generalization

(00:39:37) - Episodic memory and sociality in language models

(00:47:15) - 1000 days project and talking to crows

(00:52:14) - "Understanding" in neuroscience

Kevin Mitchell is an Associate Professor of Genetics and Neuroscience at the Trinity College Dublin. He recently published his second book, "Free Agents: How Evolution Gave Us Free Will." It's a rigorous defense for why we (and other living systems) have free will, arguing all the way from quantum indeterminacy, to C. elegans, to how humans can form abstracted meanings over very long timescales. We also go beyond the book, exploring how free will links to unresolved questions in physics about the discrepancy of microscopic laws being time-invariant and macroscopic laws having a time asymmetry (entropy increase over time). And how the 'present' does it exist and how its duration might differ for a fly vs a human. Kevin also does a great job of explaining why top-down causality and meaning are not just some mythical concepts, but how it scientifically makes sense to speak of neural activity in terms of 'what this means for the orgasm', and how coarse-gaining allows hierarchical control structures to do causal work on this 'meaning-level'. In the end, we also talk about what kind of research Kevin would like to see and advice on learning across disciplines.

Timestamps:

(00:00:00) - Intro

(00:02:40) - The Free Will skeptics

(00:12:56) - Quantum indeterminacy, the weather, and living systems

(00:23:09) - C. elegans and how evolution exploits noise

(00:38:08) - The arrow of time and the quantum mechanics of the present

(00:43:50) - 'How long' is the present for flies vs humans

(00:52:14) - Top-down causality on the biological implementation level

(01:00:03) - Meaning as functional (not epiphenomenal) and Robert Nozick's pleasure machine

(01:05:34) - Interdisciplinary science and education

Kate Jeffery is the head of the school of psychology & neuroscience at the University of Glasgow (formerly at UCL). This episode is all about grid cells (background info), which Kate was already recording in the 1990s. We discuss how grid cells' rate maps differ when the rats climb in 3D spaces. Here we cover anything from cross-species comparisons (bats, birds), to self-organizing dynamics, and symmetry breaking. Kate also shares her (maybe unpopular) thoughts that the hexagonal grid regularity is not functional but a by-product. We also get physics-y by discussing entropy, evolution, complexity and how they link to memory and the arrow of time. At the end there is career advice and some thoughts on climate change.

Not familiar with place, grid or head direction cells? Here is my 5min primer.

Timestamps:

(00:00:00) - Intro

(00:02:14) - Missing out on a Nobel Prize

(00:11:05) - Place cells & grid cells interactions

(00:15:19) - Grid cells and rats climbing in 3D

(00:27:24) - (Spatial) ecological niches of rats, bats and birds

(00:32:55) - Self-organizing dynamics

(00:35:36) - 'Speed' in navigating physical vs abstract spaces

(00:40:19) - 3D = 2D planes stitched together?

(00:46:22) - Symmetry breaking in

(00:50:20) - 'A purey geometric module' (Cheng, 1986)

(01:01:24) - Why are grid cells grid-like?

(01:05:22) - Kate's (grid cell) secrets

(01:08:18) - Entropy, evolution, and complexity

(01:17:45) - Memory as metastable states

(01:22:07) - Entropy, memory & the arrow of time

(01:25:03) - Career Advice

(01:28:35) - Climate change & sociology

(01:38:07) - New position in Glasgow

Two weeks ago, I visited the Bernstein conference in Berlin. I had lots of fun, particularly at the poster sessions, where I met William, Movitz, and Shervin. I met with each of them later and recorded the following conversations (on bark benches again^^).

William Walker (Gatsby Computational Neuroscience Unit, London) had a poster on 'Representations of State in Hippocampus Derive from a Principle of Conditional Independence'. We discuss how current deep learning struggles with generalization, lacks priors, and could benefit by learning latent conditionally independent representations (similar to place cells).

Movitz Lenninger (KTH Royal Institute of Technology, Stockholm) had a poster on 'Minimal decoding times for various shapes of tuning curves'. He was puzzled why neurons with periodic tuning curves (such as grid cells) are so rare in the brain considering their superior accuracy. He posits there may be a trade-off between accuracy and encoding time.

Shervin Safavi (Max Planck Institute for Biological Cybernetics, Tübingen) had a poster on linking efficient coding and criticality. We introduce those concepts and talk about why noise is a feature, not a bug. Shervin is also starting a new lab at TU Dresden, where he wants to understand the computational machinery of cognitive processes and he is looking for interdisciplinary-minded applicants!

Not familiar with place, grid and head direction cells? Here is my 5min primer.

(00:00:00) - Intro

(00:02:53) - William Walker

(00:32:53) - Movitz Lenninger

(00:55:04) - Shervin Safavi

An episode with my favourite podcast host, Paul Middlebrooks. Paul and I met in Berlin, and talked about his journey away from (and back into) academia and why he started his podcast BrainInspired. Yes, there is a lot of podcast meta-talk in this episode. For example, how science podcasts give you a glimpse into another field (as an outsider) and some advice for fellow podcast hosts. We also get into productivity, self-learning and some big-picture questions on what's holding neuroscience back.

(00:00:00) - Intro

(00:01:51) - Interesting conversations Paul had at the conference

(00:07:57) - The why and how of podcasting

(00:11:16) - Changing one's mind in science

(00:19:34) - Paul's NeuroAI course

(00:20:46) - Podcasts for self-learning & productivity fallacies

(00:26:15) - Podcast advice

(00:30:58) - Paul is back in academia

(00:38:48) - Neuroscience needs theory (beyond manifolds)

(00:45:50) - Saying thank you to Paul

A couple of weeks ago, I visited the ESI SyNC 2023 conference in at the Ernst Strüngmann Institute (ESI) in Frankfurt, Germany. Their topic was "Linking hypotheses: where neuroscience, computation, and cognition meet".

During the conference, I got talking to Yossi Yovel (Tel-Aviv University) about how different bat species navigate, what their vocalizations tell us about language evolution, and discussed his recent paper on whether we will ever be able to talk to animals. On the last point, I have some strong thoughts - thoughts including Wittgenstein and crows (see my own article here).

I also chat with Francisco Garcia-Rosales (ESI) on his poster about oscillations in the bat auditory and frontal cortex, and how bats and marmosets are really good animal models for speech (and maybe language).

Sarah Robins is a philosopher at Purdue University. Based of fMRI studies, many neuroscientists have grouped memory and imagination as a single phenomena. Sarah has been busy disentangling the two and we discuss how constructivist accounts of memory might have gone too far when abandoning memory traces.

David Poeppel (ESI) has a lab on auditory cognition, music, speech and language and how they map to neurobiology. Yet, going beyond that David has some intriguing thoughts on what's missing in neuroscience more generally. We dig deep into why we need a theory of memory storage/retrieval ("engram renaissance") and how to do interdisciplinary science.

https://akseliilmanen.wixsite.com/home/post/pod03

(00:00:00) - Intro

(00:01:55) - Yossi Yovel on bat navigation, calls & talking to animals

(00:44:45) - Francisco on calls and oscillations in bats and marmosets

(00:59:35) - Sarah Robins on engrams, memory & imagination

(01:39:00) - David Poeppel on why we need a theory of memory storage and retrieval

This episode, I talk to Saeedeh Sadeghi (Cornell University) and Irena Arslanova (Royal Holloway - London) about the heart and time perception. If you have ever been in a car accident, you might have felt as if time was slowing down. Some previous studies have tried to explain this phenomenon and argued that a state of 'arousal' may slow down time (subjectively). It's a bit more complicated than that. This year, Saeedeh and Irena published two papers showing how not average heart rate but heart dynamics on the sub-second scale influence time perception. Within a single cardiac cycle, time may contract and expand. We go in-depth on the methodology and findings of their papers and make links to interoception, predictive coding, meditation, breathing, psychoactive substances, and the many time perception theories out there. At the end, we also talk about science communication and their future research plans.

Full show notes (with extra figures):

https://akseliilmanen.wixsite.com/home/post/pod02

Timestamps:

(00:00:00) - Saeedeh's and Irena's background

(00:05:09) - Does 'arousal' slow down time?

(00:12:20) - Virtual Reality subway study

(00:15:58) - Orienting response in evolution and pregnancy

(00:20:57) - Phenomenology of orienting response vs meditation

(00:27:52) - Temporal bisection task & methodology

(00:35:55) - Heart anatomy, systole and diastole explained

(00:40:34) - Subjective time contracts and expands within each heartbeat

(00:53:28) - How sub-second heart dynamics interact with average heart rate

(01:02:43) - Oscillations & striatal beat frequency model

(01:08:24) - Individual differences in interoception and heart-rate variability

(01:12:16) - Heart-brain communication & the insula as an integrator

(01:26:32) - Question by Josh Goheen on how breathing modulates the heart

(01:32:19) - Psychoactive substances and slowing of breath

(01:37:11) - Neural time perception theories (Roseboom, Tsao, Buonomano)

(01:46:41) - Time tracking in retrospective and prospective memory

(01:50:53) - Science communication with the public & future directions

(01:59:53) - Outro

Saeedeh Sadeghi

Irena Arslanova

Josh Goheen

My BSc dissertation: Graph-driven comparative phenomenology of altered time perception in over 20,000 trip reports URL

Other books/papers mentioned:

Marc Wittmann (2017): Felt Time: The Science of How We Experience Time book

Claudia Hammond (2013): Time Warped: Unlocking the Mysteries of Time Perception book

Craig, 2009: Emotional moments across time: a possible neural basis for time perception in the anterior insulas paper

Sarigiannidis et al., 2020: Anxiety makes time pass quicker while fear has no effect paper

Corcoran et al., 2023: Visceral afferent training in action paper

Review paper on striatal beat frequency model (2016)

Friston, 2018: Am I Self-Conscious? (Or Does Self-Organization Entail Self-Consciousness?) paper

Roseboom et al., 2019: Activity in perceptual classification networks as a basis for human subjective time perception paper

Tsao et al., 2022: The neural bases for timing of durations paper

Buonomano & Maass, 2009: State-dependent computations: spatiotemporal processing in cortical networks paper

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In the first episode of the Brain Space Time Podcast, I talk to Georg Northoff, a neuroscientist, psychiatrist and philosopher based in Ottawa, Canada. Georg argues that the self and time are fundamental to how the brain constructs a model of the world. We start off with the role of spontaneous activity in the brain, including the role of the default mode network, although Georg might convince you that you shouldn't think of it as one of many networks but as a baseline. We also dig deep into philosophy, going back to Kant, Leibniz and even Heraclitus. Georg argues that we should drop the mind-body problem, and move to the world-brain problem instead. Central to the world-brain problem is the ability of our brain to match the temporal-spatial statistics of its environment, "aligning with the grove of the music"; as Georg would say. Here we get into physics territory by discussing this matching mechanism in terms of self-similarity, scale-free dynamics, and the differential effects of pink and white noise on the brain. Evolution is also a recurring theme, as we get into the types of self across species, long-distance navigation of whales or ask how the temporal statistics of neuronal activity are conserved across species despite them having varied ecological niches. A big part of the episode is on time perception and temporal scales, exploring how time perception is too slow for depressed patients or how our breathing and heart rate are reflected in neuronal and mental dynamics. Finally, Georg tells us about the benefits but also struggles of his interdisciplinary career trajectory.

Shownotes and mentioned figures available at:

https://akseliilmanen.wixsite.com/home/post/pod01

Timestamps:

(00:00) - Intro

(02:54) - How did you get interested in time and the self

(06:31) - Spontaneous activity as psychological baseline of the brain

(13:14) - Default mode network, cortical midline structures, and the self

(17:04) - Interoception, bodily self across species and mirror-self recognition

(25:21) - From mind-body to world-brain problem, dissolving philosophical concepts (i.e. Élan vital)

(38:25) - Why physicists get spatiotemporal neuroscience and working memory psychologists don't

(44:28) - The brain matches the spatiotemporal statistics of its world

(54:05) - Scale-free dynamics and the neural response to white/pink noise in conscious/unconscious states

(01:01:25) - Neuronal rhythms across species (Buzaski), temporal receptive windows (Hasson)

(01:17:35) - Time perception & time scales in heart rate and breathing

(01:27:49) - Time perception impairment in depression and mania

(01:31:51) - Time perception & time scales - how to manipulate/disentangle them

(01:37:20) - Difference based coding - bigger than predictive coding?

(01:43:05) - Interdisciplinary career trajectory - benefits & challenges

(01:56:25) - Advice for computational neuroscientists

(02:01:04) - Where is spatiotemporal neurosciences in 10 years & what are the challenges

Links/Books/Papers

Georg Northoff website

Book: Neurowaves - Brain, Time and Consciousness (2023) URL

Book: The Spontaneous Brain (2018) URL

Textbook: From Brain Dynamics to the Mind: Spatiotemporal neuroscience (2023 - pre-order) URL

Self and cortical midline structures (2004) paper

Heart, lung, and brain - Josh Goheen (2023) paper

Brain and intrinsic neural timescales paper with Mehrshad Golesorkhi (2023) paper

Spatiotemporal neuroscience as 'common currency' (2020) paper

Why Spatiotemporal neuroscience (2020) paper

Are object relations temporal? (2022) paper

Leibniz and dynamic time (2019) paper

Marcus Raichle- default mode network 2001 paper, 2015 paper

Gyuri Buzaski (2013) - neuronal rhythms across species

Uri Hasson (2015) - temporal receptive windows paper

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If you are interested in my other work, click here.

Music license

Song: Space News (URL)

Item License Code: Z62T4V3QWL

In this short episode, I give a rough outline of what the Brain Space Time podcast will be about!

(00:00) - What is the Brain Space Time Podcast about?

(01:39) - The podcast logo explained. 

(05:28) - Getting in touch. 

Links

Show notes for this episode (with Bergson's cone figure)

Henri Bergson's 1986 Matter and memory PDF (Cone figure on p. 61)

Uri Hasson on temporal receptive windows paper 

For updates on new episode releases, follow me on Twitter.

I welcome your comments, questions, and suggestions. Feel free to email me at [email protected]

If you are interested in my other work, click here to look at my other podcast, blog, website, or (ongoing) Bachelor dissertation on time perception semantic networks.