Frequent lucid dreaming associated with increased functional connectivity between frontopolar cortex and temporoparietal association areas

Introduction

Definition of Lucid Dreaming

a special sort of dream in which you know that
you are dreaming while still in the dream

during lucid dreams

metacognitive awareness of one’s state of consciousness

regain episodic memory for waking life

variation in lucid dream frequency, ranging

the question of whether the frequency of lucid dreams is related to individual differences in anatomical or functional properties of the brain

Hypoactivity of The prefrontal cortex, parietal cortex and lateral middle temporal cortex

underlie the diminished self-awareness and volitional control during dreaming

increased BOLD signal during lucid dream

aPFC, IPL, precuneus and ITG/MTG

no group-level fMRI

evidence linking frontopolar and parietal regions to lucid dreaming is consistent with the role of these regions in metacognitive functions

further support of a connection between the metacognitive functions of aPFC and lucid dreaming

frontopolar cortex (BA9/10)

increased gray matter volume

increased BOLD activation

to test whether differences in brain structure and/or functional connectivity are associated with frequent lucid dreams while also controlling for dream recall frequency

participants

28 right-handed participants (18 females, age = 22.6 ± 5.4 (mean ± SD), range 18–34)

frequent lucid dream group

control

a minimum of 3–4 lucid dreams per week, or approximately one lucid dream every other night without engaging in training to have lucid dreams

the same age (date of birth <12 months apart), the same gender, a similar level of dream recall and lucid dream frequency of 1 per year or less

問卷

dream recall (0-15pt)

dream frequency (0-15pt)

口試

the number of lucid dreams they had in the last 6m

the most lucid dreams they had ever had in a six-month period

training or not

dream recall

3pt內

dream recall frequency 差異在1-2個夢

Behavioral and questionnaire assessment

association of lucid dreaming and PFC function

working memory capacity

trait mindfulness

prospective and retrospective memory

operation span task (OSpan)

rotation span task (RotSpan)

symmetry span task (SymSpan)

to-be-remembered stimuli are letters

unrelated task is verifying the accuracy of an equation

locations of red squares in a 4 × 4 grid

verifying the vertical symmetry of an image

arrows pointing in one of eight different directions

whether a rotated letter is presented correctly

Toronto Mindfulness Scale

Curiosity

Decentering

an attitude of wanting to learn more about one’s experiences

awareness of one’s experience with some distance and dis-identification rather than being carried away by one’s thoughts and feelings

Prospective and Retrospective Memory Questionnaire (PRMQ)

Mind-wandering frequency

Daydreaming Frequency subscale of the Imaginal Process Inventory (IPI)

experience daydreaming in their daily life with reference to a five-point Likert-scale, ranging from “A” to “E.”

measures self-report scores of the frequency of both prospective and retrospective memory errors in everyday life

均無顯著差異

Voxel-based morphometry

a voxel-wise comparison of local tissue volumes within a group or across groups

No significant differences in gray matter density were observed for ROIs

Voxel intensities represents the relative volume at that voxel

left & right prefrontal cortex

left or right hippocampus

total hippocampus

by reference

Seed-based whole-brain resting-state functional connectivity

To estimate connectivity

Based on the time series of a seed voxel (or ROI), connectivity is calculated as the correlation of time series for all other voxels in the brain.

brain areas with similar activity patterns are likely to be communicating and sharing information.

the frequent lucid dream group showed significantly increased functional connectivity between left aPFC and five clusters

the left and right inferior parietal lobule (IPL)

left and right middle temporal gyrus (MTG)

right inferior frontal gyrus (IFG)

reduced functional connectivity

bilateral insula

other regions identified in ref. 9 to increase BOLD signal during lucid REM sleep

frequent lucid dream group showed increased connectivity

left IPL and left MTG, right lingual gyrus

right IPL and left aPFC, right PCC

right MTG and left aPFC, left MFG

decreased connectivity

right IPL and right MFG, left insula

left precentral gyrus and left SMC

IPL/IPS subdivision analysis

to characterize the overlap between these clusters and anatomical subdivisions of the angular gyrus (PGa/ PGp) and intra-parietal sulcus (hlP1, hlP2 and hlP3)

The subdivisions of AG and IPS have been shown to have distinct structural and functional connectivity patterns

Frequent lucid dreamers showed significantly increased mean functional connectivity

left aPFC and left PGa

right PGa and right hlP1

PGa

PGp

hIP1

hIP2

hIP3

basal ganglia

ventral premotor areas

ventrolateral prefrontal cortex

ventromedial prefrontal cortex

posterior cingulate

hippocampus-regions comprising the default mode network.

ventral premotor

ventral premotor

middle frontal gyrus

middle frontal gyrus

insula

extrastriate visual areas

Large-scale networks (LSNs) analysis

compare whether connectivity within and between established large scale resting-state brain networks showed differences between groups

7 systems

default mode network

cingulo-opercular

frontoparietal control network

salience network

ventral attention network

dorsal attention network

visual system

evaluating the connectivity between all nodes within the frontoparietal control subsystem that showed the largest overlap with the functional connectivity results, based on a 400 node parcellation of the 17 functional network

within any LSN between groups

between-network connectivity between groups

no differences

no differences

connectivity within the FPCN subsystem between groups

no differences

Whole-brain graph-theoretic analysis

To evaluate whole-brain differences in network and topological properties

degree (k)

strength (s)

betweenness centrality (BC)

eigenvector centrality (EC)

total number of connections of a node

the sum of the weights of all connections to a node

the length between nodes

fraction of all shortest paths in the network that contain a given node

nodes connected to other densely connected nodes as having high centrality

connection density (δ)

the number of existing connections over the total number of possible connections

frequent lucid dream group is higher

frequent lucid dream group is higher

No differences

No differences

more closely linked to the semantic system than PGp

higher-order thinking that enables understanding, analysis, and control of one’s cognitive processes, especially when engaged in learning.

hIP2 and hIP1) may support more complex aspects of numerical and mathematical information processing

舉例

了解清醒夢的定義