Neuroscience is full of open questions. The most fundamental come down to space and time. What can place cells, grid cells and cognitive maps tell us about the evolutionary history from spatial navigation to abstract cognition? Do temporal dynamics between neural oscillations of different frequencies explain how information is structured in the brain? And are there species differences in how time is perceived? To find answers, or at least better questions, I am interviewing researchers in neuroscience, philosophy and physics.
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#8 Uri Hasson: Language in the real world for brains and AI
Saison 1 · Épisode 1
mercredi 13 décembre 2023 • Durée 56:54
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.
Hasson et al., 2015 - Hierarchical process memory: memory as an integral component of information processing Temporal receptive windows paper
Hasson et al., 2020 - Direct Fit to Nature: An Evolutionary Perspective on Biological and Artificial Neural Networks paper
Yeshurun et al., 2021 - The default mode network: where the idiosyncratic self meets the shared social world paper
Goldstein et al., 2022 - The Temporal Structure of Language Processing in the Human Brain Corresponds to The Layered Hierarchy of Deep Language Models preprint
Nguyen et al., 2022 - Teacher student neural coupling during teaching and learning paper
Goldstein et al., 2022 - Shared computational principles for language processing in humans and deep language models paper
Also mentioned:
Podcast episode with Tony Zador on Genomic Bottlenecks link
(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
#7 Kevin Mitchell: Free Agents (in an evolving block universe)
Saison 1 · Épisode 7
mardi 5 décembre 2023 • Durée 01:20:26
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.
Mitchell, 2020 - Innate: How the Wiring of Our Brains Shapes Who We Are book
Potter et al., 2022 - Naturalising Agent Causation paper
Mitchell, 2023 - The origins of meaning – from pragmatic control signals to semantic representations preprint
#6 Kate Jeffery: Grid cells in 3D, entropy & climate change
Saison 1 · Épisode 6
mardi 17 octobre 2023 • Durée 01:43:27
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.
For Apple Podcast users, find books/papers links at: https://akseliilmanen.wixsite.com/home/post/pod06
Not familiar with place, grid or head direction cells? Here is my 5min primer.
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!
For Apple Podcast users, find books/papers links at: https://akseliilmanen.wixsite.com/home/post/pod05
Not familiar with place, grid and head direction cells? Here is my 5min primer.
William's publications:
#4 Paul Middlebrooks: BrainInspired & Podcasting
Saison 1 · Épisode 4
mardi 3 octobre 2023 • Durée 47:01
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.
For Apple Podcast users, find books/papers links at: https://akseliilmanen.wixsite.com/akseli-ilmanen/post/pod04
#3 ESI SyNC 2023: Bats, memory & interdisciplinary science
Saison 1 · Épisode 3
mardi 26 septembre 2023 • Durée 02:12:00
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.
For Apple Podcast users, find books/papers links at:
#2 Saeedeh Sadeghi & Irena Arslanova: Heart and time perception
Saison 1 · Épisode 2
vendredi 18 août 2023 • Durée 02:01:03
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
(00:35:55) - 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
#1 Georg Northoff: Spatiotemporal neuroscience
Saison 1 · Épisode 2
vendredi 14 juillet 2023 • Durée 02:14:10
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
Welcome to the Brain Space Time Podcast!
Saison 1
lundi 6 février 2023 • Durée 05:47
In this short episode, I give a rough outline of what the Brain Space Time podcast will be about!
Timestamps:
(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)
For updates on new episode releases, follow me on Twitter.
I welcome your comments, questions, and suggestions. Feel free to email me at akseli.ilmanen@gmail.com
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.
#9 Hugo Merchant: Neuronal population clocks
Saison 1 · Épisode 9
mardi 1 octobre 2024 • Durée 44:19
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
Lenninger et al., 2022 - How short decoding times, stimulus dimensionality and spontaneous activity constrain the shape of tuning curves: A speed-accuracy trade-off preprint
Lenninger et al., 2023 - Are single-peaked tuning curves tuned for speed rather than accuracy? paper
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