Introductory slides to CNS 2019 Mental Models of Time Our symposium will focus on current working hypotheses suggesting that the construction of ordinal sequences and temporal reasoning may be necessary for an intelligible and conscious representation of time. Recent neuroscientific work suggests that algorithms dedicated to the mapping of space may also serve the mapping of time (Buzsáki & Moser, Nat Neurosci 2013). However, a great majority of studies focuses on the individual physically or virtually moving in its environment, so that the traversed spatial and temporal dimensions of the world fully correlate (as a function of the animal’s speed). As part of a dedicated navigational system, time and speed cells may contribute to the mapping of time (Kropff et al, 2015; Tsao et al, 2018), but what happens to our mental representation of time when the body does not move? Is memory retrieval sufficient to build the psychological arrow of time, past, present and future? To which extent ordering information along the time dimension may, or not, require dedicated operations as compared to imagining spatial representations? In this symposium, we will discuss recent empirical work focus on how memorized events and their temporal structure are endogenously manipulated, and ordered to build conscious narratives possibly feeding a mental model of time.

1. Mental Models of Time ?
Marc Howard
Dept of Psychological and
Brain Sciences
Dept of Physics
Boston University, USA
Christian Doeller
Max-Planck-Institute for Human
Cognitive and Brain Sciences,
Leipzig, Germany;
Kavli Institute for Systems
Neuroscience, NTNU,
Trondheim, Norway
Charan Ranganath
Center for Neuroscience
Dept of Psychology
University of California at
Davis, USA
Virginie
van Wassenhove
CEA NeuroSpin
INSERM Cognitive
Neuroimaging Unit
Gif sur Yvette, France

2. What is a Mental Model? Kenneth Craik (1943)
Human thought has a definite function: it provides a convenient small-scale model of a
process so that we can, for instance, design a bridge in our minds and know that it will bear a
train passing over it instead of having to conduct a number of full scale experiments […]

3. Computations [what we are trying to solve]
• Why would the brain need to represent time?
• Why do we experience a past-to-future orientation?
Algorithm [rules and representations]
• What is a representation for time?
• How does the brain endogenously (re)structure events in time?
Implementation [neurobiology]
• Is time stored and retrieved?
• Is time a process of reconstruction?
+ their inter-relations
Mental Model of Time
using David Marr’s heuristics (1982)

4. Is time memory?
Time & Timing Memory
explains online experiencing of the now explains past and future
experienced prospectively remembered retrospectively
memory of intervals, elapsed times, quantities,
durations
memory of events, episodes, their context
what where when who
hierarchical time implemented as
rhythms
spatialized time
scanning models, mental time line
[…] […]
Eichenbaum (2018) Neuron

5. Mental Models of Time
a dialogue between communities
McTaggart (1903) A & B series
Buonomano (2017)

6. 1. We experience time as a timeline with a past and a future.
2. My students and I have worked out a computational model for how the
brain might do that.
3. Neurophysiology confirms many predictions of this model.
4. We've since worked out ways to construct a future; people should test
these predictions.
10:08 - 10:34 am Neurons in many brain regions show firing properties consistent
with a compressed neural timeline of recent experience.
Singh et al (2018)
Neurobio Learn & Mem
Howard (2018) TiCS
Marc Howard
Dept of Psychological & Brain Sciences
Dept of Physics, Boston University, USA

7. 10:34 - 11:00 am
We understand and reconstruct
events in large part through their
temporal structure, but temporal
structure is poorly understood -
the dark matter in episodic
memory research.
Charan Ranganath
Center for Neuroscience, Dept of
Psychology, UC Davis, USA
1. The hippocampus represents sequences
of experiences within an event
2. The Posterior Medial Network represents
long timescale information about the
context of an event
3. The Medial Prefrontal Cortex represents
information about classes of events that
may enable representation of episodes
PM
Network
vmPFC
Hippocampus
PM
Network
PM
Network
Hippocampus Hippocampus
Episode
Event
Items in Event
Context

8. 11:00 - 11: 26 am
Our findings suggest a dissociation between
objective and subjective temporal maps in EC
and hippocampus; thereby providing novel
evidence for the role of the hippocampal-
entorhinal region in representing time for
episodic memory.
Christian Doeller
Max-Planck-Institute for Human Cognitive and Brain
Sciences, Leipzig, Germany; Kavli Institute for
Systems Neuroscience, NTNU, Trondheim, Norway
1. aLEC encodes objective time
2. Hippocampus encodes subjective time

9. 11:26 - 11: 52 am
1. Time, unlike space, is experienced and thought of as a unidirectional flow.
Yet, time is often conceived as space in the brain (metaphor, magnitude,
scanning a mental time line,…)
2. We studied what cannot be studied in animals: humans thinking about
themselves away from the « here and now »
Moving through space takes time, moving through time doesn’t take space.
- WK Honig (1981) in Information Processing in Animals
Virginie van Wassenhove
CEA NeuroSpin; INSERM Cognitive
Neuroimaging Unit Gif sur Yvette, France