Presentations

Abstract

How do human cultural inventions such as reading result in neural re-organization? Previous cross-sectional studies have reported extensive effects of literacy on the neural systems for vision and language (Dehaene et al [2010, Science], Castro-Caldas et al [1998, Brain], Petersson et al [1998, NeuroImage], Carreiras et al [2009, Nature]). In this first longitudinal study with completely illiterate participants, we measured brain responses to speech, text, and other categories of visual stimuli with fMRI before and after a group of illiterate participants in India completed a literacy training program in which they learned to read and write Devanagari script. A literate and an illiterate no-training control group were matched to the training group in terms of socioeconomic background and were recruited from the same societal community in two villages of a rural area near Lucknow, India. This design permitted investigating effects of literacy cross-sectionally across groups before training (N=86) as well as longitudinally (training group N=25). The two analysis approaches yielded converging results: Literacy was associated with enhanced, mainly left-lateralized responses to written text along the ventral stream (including lingual gyrus, fusiform gyrus, and parahippocampal gyrus), dorsal stream (intraparietal sulcus), and (pre-) motor systems (pre-central sulcus, supplementary motor area), thalamus (pulvinar), and cerebellum. Significantly reduced responses were observed bilaterally in the superior parietal lobe (precuneus) and in the right angular gyrus. These positive effects corroborate and extend previous findings from cross-sectional studies. However, effects of literacy were specific to written text and (to a lesser extent) to false fonts. Contrary to previous research, we found no direct evidence of literacy affecting the processing of other types of visual stimuli such as faces, tools, houses, and checkerboards. Furthermore, unlike in some previous studies, we did not find any evidence for effects of literacy on responses in the auditory cortex in our Hindi-speaking participants. We conclude that learning to read has a specific and extensive effect on the processing of written text along the visual pathways, including low-level thalamic nuclei, high-level systems in the intraparietal sulcus and the fusiform gyrus, and motor areas. The absence of an effect of literacy on responses in the auditory cortex in particular raises questions about the extent to which phonological representations in the auditory cortex are altered by literacy acquisition or recruited online during reading.

Abstract

To what extent is visual attention driven by the semantics of individual objects, rather than by their visual appearance? To investigate this we continuously measured eye movements, while observers searched through displays of common objects for an aurally instructed target. On crucial trials, the target was absent, but the display contained object s that were either semantically or visually related to the target. We hypothesized that timing is crucial in the occurrence and strength of semantic influences on visual orienting, and therefore presented the target instruction either before, during, or af ter (memory - based search) picture onset. When the target instruction was presented before picture onset we found a substantial, but delayed bias in orienting towards semantically related objects as compared to visually related objects. However, this delay disappeared when the visual information was presented before the target instruction. Furthermore, the temporal dynamics of the semantic bias did not change in the absence of visual competition. These results po int to cascadic but independent influences of semantic and visual representations on attention. In addition. the results of the memory - based search studies suggest that visual and semantic biases only arise when the visual stimuli are present. Although we consistent ly found that people fixate at locat ions previously occupied by the target object (a replication of earlier findings), we did not find such biases for visually or semantically related objects. Overall, our studies show that the question whether visual orienting is driven by semantic c ontent is better rephrased as when visual orienting is driven by semantic content.

Abstract

I will discuss recent research with illiterates and individuals with dyslexia which suggests that many cognitive ‚defi ciencies‘ proposed as possible causes of dyslexia are simply a consequence of decreased reading experience. I will argue that in order to make further progress towards an understanding of the causes of dyslexia it is necessary to appropriately distinguish between cause and effect.

Abstract

How do human cultural inventions such as reading result in neural re-organization? In this first longitudinal study with young completely illiterate adult participants, we measured brain responses to speech, text, and other categories of visual stimuli with fMRI before and after a group of illiterate participants in India completed a literacy training program in which they learned to read and write Devanagari script. A literate and an illiterate no-training control group were matched to the training group in terms of socioeconomic background and were recruited from the same societal community in two villages of a rural area near Lucknow, India. This design permitted investigating effects of literacy cross-sectionally across groups before training (N=86) as well as longitudinally (training group N=25). The two analysis approaches yielded converging results: Literacy was associated with enhanced, left-lateralized responses to written text along the ventral stream (including lingual gyrus, fusiform gyrus, and parahippocampal gyrus), dorsal stream (intraparietal sulcus), and (pre-) motor systems (pre-central sulcus, supplementary motor area) and thalamus (pulvinar). Significantly reduced responses were observed bilaterally in the superior parietal lobe (precuneus) and in the right angular gyrus. These effects corroborate and extend previous findings from cross-sectional studies. However, effects of literacy were specific to written text and (to a lesser extent) to false fonts. We did not find any evidence for effects of literacy on responses in the auditory cortex in our Hindi-speaking participants. This raises questions about the extent to which phonological representations are altered by literacy acquisition.

Abstract

How do human
cultural
inventions
such as reading
result
in neural
re-organization?
In this first longitudinal
study
with young
completely
illiterate
adult
participants,
we measured
brain
responses
to speech,
text, and other
categories
of visual
stimuli
with fMRI
before
and after a group
of
illiterate
participants
in India
completed
a literacy
training
program
in which
they learned
to read and write
Devanagari
script.
A literate
and an illiterate
no-training
control
group
were
matched
to the
training
group
in terms
of socioeconomic
background
and were
recruited
from
the same
societal
community
in two villages
of a
rural area near Lucknow,
India.
This design
permitted
investigating
effects
of literacy
cross-sectionally
across
groups
before
training
(N=86)
as well as longitudinally
(training
group
N=25).
The two
analysis
approaches
yielded
converging
results:
Literacy
was
associated
with enhanced,
left-lateralized
responses
to written
text
along
the ventral
stream
(including
lingual
gyrus,
fusiform
gyrus,
and parahippocampal
gyrus),
dorsal
stream
(intraparietal
sulcus),
and (pre-)
motor
systems
(pre-central
sulcus,
supplementary
motor
area)
and thalamus
(pulvinar).
Significantly
reduced
responses
were observed
bilaterally
in the superior
parietal
lobe (precuneus)
and in the right angular
gyrus.
These
effects
corroborate
and extend
previous
findings
from
cross-sectional
studies.
However,
effects
of literacy
were
specific
to written
text and (to a lesser
extent)
to
false fonts.
We did not find any evidence
for effects
of literacy
on
responses
in the auditory
cortex
in our Hindi-speaking
participants.
This
raises
questions
about
the extent
to which
phonological
representations are altered by literacy acquisition.

Abstract

c

Abstract

c

Abstract

Recent empirical evidence suggests that language-mediated eye gaze around the visual world varies across individuals and is partly determined by their level of formal literacy training. Huettig, Singh & Mishra (2011) showed that unlike high-literate individuals, whose eye gaze was closely time locked to phonological overlap between a spoken target word and items presented in a visual display, low-literate individuals eye gaze was not tightly locked to phonological overlap in the speech signal but instead strongly influenced by semantic relationships between items. Our present study tests the hypothesis that this behaviour is an emergent property of an increased ability to extract phonological structure from the speech signal, as in the case of high-literates, with low-literates more reliant on syllabic structure. This hypothesis was tested using an emergent connectionist model, based on the Hub-and-spoke models of semantic processing (Dilkina et al, 2008), that integrates linguistic information extracted from the speech signal with visual and semantic information within a central resource. We demonstrate that contrasts in fixation behaviour similar to those observed between high and low literates emerge when the model is trained on either a speech signal segmented by phoneme (i.e. high-literates) or by syllable (i.e. low-literates).