Adult subcortex processes numbers with the same skill as infants

March 20, 2017, Carnegie Mellon University
Despite major brain differences, many species from spiders to humans can recognize and differentiate relative quantities. Adult primates, however, are the only ones with a sophisticated cortical brain system, meaning that the others rely on a subcortex or its evolutionary equivalent.Carnegie Mellon University scientists wanted to find out whether the adult human subcortex contributes to number processing at all. Published in the Proceedings of the National Academies of Sciences, their study found that the adult subcortex processes numbers at the same level as infants and perhaps other lower-order species, such as guppies and spiders. Credit: Melissa Neely for Carnegie Mellon University

Despite major brain differences, many species from spiders to humans can recognize and differentiate relative quantities. Adult primates, however, are the only ones with a sophisticated cortical brain system, meaning that the others rely on a subcortex or its evolutionary equivalent.

Carnegie Mellon University scientists wanted to find out whether the adult human subcortex contributes to number processing at all. Published in the Proceedings of the National Academy of Sciences, their study found that the adult subcortex processes numbers at the same level as infants and perhaps other lower-order species, such as guppies and spiders.

"This study tells us a great deal about the human subcortex, most importantly that it does not appear to improve from its number abilities in infancy, while the cortex, which is more developed in humans than in any other species, does continuously develop," said Elliot Collins, a Ph.D. student in psychology within CMU's Dietrich College of Humanities and Social Sciences and a M.D. student in the School of Medicine at the University of Pittsburgh.

Because the subcortex's location and small size make it hard to observe in humans using imaging techniques, the researchers conducted a series of experiments using a stereoscope. The stereoscope allowed them to present two consecutive visual stimuli either sequentially to one eye at a time or sequentially to both eyes. This was crucial since signals that enter one eye remain separated in the subcortical part of the visual system.

One hundred made decisions about two groups of dots to the same eye or different eyes. The results showed that numerical judgments in the one eye trials were better under one key condition: when the first and second stimuli's quantity differed greatly, such as having a ratio of 4:1 or 3:1.

"The subcortex is not good at making fine grain number discriminations, and these findings support that," Collins said. "Our results suggest, however, that adults with a fully operational cortex still have a subcortex with the ability to distinguish , yet it operates on a similar level to what is found in babies, other primates and lower level species who can make coarse computations of large ratios such as, for example, which shoal of fish is bigger and should be joined. This provides evidence of a potential evolutionary bridge between the human adult subcortex and the brain of lower order ."

CMU's Marlene Behrmann, the Cowan University Professor of Cognitive Neuroscience, and the University of Massachusetts' Joonkoo Park, who received his master's in human-computer interaction from CMU, also participated in the study.

Explore further: Subcortical damage is 'primary cause' of neurological deficits after 'awake craniotomy'

More information: Numerosity representation is encoded in human subcortex, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1613982114

Related Stories

Subcortical damage is 'primary cause' of neurological deficits after 'awake craniotomy'

February 7, 2013
Injury to the subcortical structures of the inner brain is a major contributor to worsening neurological abnormalities after "awake craniotomy" for brain tumors, reports a study in the February issue of Neurosurgery, official ...

Neuronal feedback could change what we 'see'

March 30, 2016
Ever see something that isn't really there? Could your mind be playing tricks on you? The "tricks" might be your brain reacting to feedback between neurons in different parts of the visual system, according to a study published ...

Researcher develops mouse model for studying development of visual cortex

November 30, 2016
A day by day log of cortical electric activity in the mouse visual cortex was published in the Journal of Neuroscience by George Washington University (GW) researcher Matthew Colonnese, Ph.D. This research is the first to ...

Neuroscientists identify how the brain works to select what we (want to) see

February 21, 2012
If you are looking for a particular object — say a yellow pencil — on a cluttered desk, how does your brain work to visually locate it?

Recommended for you

Research reveals atomic-level changes in ALS-linked protein

January 18, 2018
For the first time, researchers have described atom-by-atom changes in a family of proteins linked to amyotrophic lateral sclerosis (ALS), a group of brain disorders known as frontotemporal dementia and degenerative diseases ...

Fragile X finding shows normal neurons that interact poorly

January 18, 2018
Neurons in mice afflicted with the genetic defect that causes Fragile X syndrome (FXS) appear similar to those in healthy mice, but these neurons fail to interact normally, resulting in the long-known cognitive impairments, ...

How your brain remembers what you had for dinner last night

January 17, 2018
Confirming earlier computational models, researchers at University of California San Diego and UC San Diego School of Medicine, with colleagues in Arizona and Louisiana, report that episodic memories are encoded in the hippocampus ...

Recording a thought's fleeting trip through the brain

January 17, 2018
University of California, Berkeley neuroscientists have tracked the progress of a thought through the brain, showing clearly how the prefrontal cortex at the front of the brain coordinates activity to help us act in response ...

Midbrain 'start neurons' control whether we walk or run

January 17, 2018
Locomotion comprises the most fundamental movements we perform. It is a complex sequence from initiating the first step, to stopping when we reach our goal. At the same time, locomotion is executed at different speeds to ...

Neuroscientists suggest a model for how we gain volitional control of what we hold in our minds

January 16, 2018
Working memory is a sort of "mental sketchpad" that allows you to accomplish everyday tasks such as calling in your hungry family's takeout order and finding the bathroom you were just told "will be the third door on the ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.