Neurosensory Integration and the Visual Hierarchy
“It has not been easy for the helping professions to conceive of human behavior as an expression of the brain, and they are still struggling to do so… The employing of neural mechanisms to enhance motor development is now well established; the current area of major growth and controversy lies in the use of neurological constructs to aid in understanding and ameliorating cognitive functions such as learning disabilities…” A. Jean Ayres Ph.D (1974) quoted in Wikipedia (July 30, 2012).
Early childhood education is unique in that it requires, more than at any other time, that the child learn how to learn. Since learning in school is primarily through recognition and interpretation of visual signals, that is to say ‘reading’, learning to learn consists primarily of developing skills around visual interpretation written language. Reading and writing do not arise spontaneously through ontogeny, but require exposure to the underlying ideas in a guided fashion. This training must consist of developing a sense of how sights and sounds are matched to make language, and this is not restricted to only auditory-visual stimuli parings, but is heavily dependent upon a more primitive underlying neurosensory and neuromuscular foundation, which must be robust for higher-level functions and skills to arise.
To the clinician, neurosensory development and integration are clearly fundamental in supporting the evolution of natural language and learning abilities. Assessment of sensory and sensory-motor integrative status provides insight into the obstacles before the child, and helps to direct efforts in therapy: Are the concerns more developmental or more functional in nature? In other words, the child has either not had the opportunity to develop the necessary foundation to learning, in the former case, or the current skills do not permit performance at the required level of achievement even though developmentally all might be in order, in the latter case.
It is now apparent that sensory deficits can occur intra-modally, with some degree of impairment to function in one sensory system, or inter-modally with trouble present in the integration of multiple senses and motor feedback systems. Integrative disorders consist of errors in improper matching of stimuli at a neural level, as well as impeded conduction between brain areas. One way of looking at this is there is a difficulty in matching spatially oriented stimuli (sights) with temporally sequenced stimuli (sounds) at a high level of sensory/perceptual processing. When this stimulus pairing does not occur, or occurs with difficulty, more primitive methods of dealing with language will be adopted – labored and delayed speech, stunted reading, mechanical as opposed to fluid reading, reliance on decoding words as opposed to recognition of whole words.
There is some question as to how to classify sensory disintegrative disorders in diagnostic manuals. Whether Sensory Integration Disorder (SID), Sensory Processing Disorder (SPD), or ‘Regulation Disorders of Sensory Processing’, a growing body of developmental professionals recognize the ontogenic impact of limited early sensory and sensory-motor experiences. Regardless of a child’s innate abilities, lack of such exposure will limit their growth and potential. Putting the nosology of sensory disintegrative disorders aside, it is clear that that sensory integration deficits need to be addressed clinically; indeed, we cannot expect any significant outcomes from our therapeutic efforts unless we address the core either at the outset, or concurrently with other therapies.
Notes on Sensory and Sensory-Motor Integration
Our senses perceive both passively and actively, depending on whether we are attending to a stimulus or not. On a very low level, we have no control over the body’s responses to certain stimuli, such as when the eye closes when it is touched. Our higher cognitive functions can override some responses, however, through through training and experience. Between low-level sensation and high-level cognition lies perception. Perception evolves from integrated sensory inputs, but is tempered by cognitive functions, such as attention, memory, and expectation. These latter can override or influence the final overall experience and perception of what is occurring. (See Dr. Lea Hyvarinen ‘s outline of visual functions in Principles Part I, as well as Part III for an idea of what these intermediate visual perceptual functions are.)
Ontogenesis of sensory dominance moves from proximoceptive inputs (physical contact) to telereceptive sensation (visual and auditory which can be used at a distance, without physical contact). Rather than reaching out, grabbing, feeling, and tasting the environment as infants, we learn to recall these sensations and the same understanding by simply visually recognizing the objects of interest, and later in school, the symbols of language. In other words, vision and audition become short hand for early forms of information gathering and interaction with the environment, with vision the predominant modality in healthy well-developed children. In the classroom, some 80% of information is gleaned through visual scanning and processing. Still, strong auditory and visual processing are not sufficient to ensure success in reading, a child must have strong and automatic integration of skills and sensory-motor responses.
Initially, in the global phase of sensory development, sensory stimuli are subject to modal specificity, that is, sensations exist simultaneously, but are not well integrated. The nature of the structure of the nervous system encourages intermodal integration, and this occurs more readily after the individual modalities have matured in their own right. Perception and sensory integration are first supported by kinethesis. Intersensory development that impacts on learning is not limited to Auditory-Visual stimuli, but extends to visual-tactile-kinesthetic as well. VTK provides a foundation for the development of visual integration later on. Auditory-Visual integration is, however, a sensitive integrative task that is reflective of a child’s total development. Therefore, assessment of visual skills from an early age provides an effective means of monitoring a child’s progress and relative risk.
The ability to equate a temporally distributed auditory stimulus to spatially distributed visual response is one factor that distinguishes strong readers from those who struggle. We can also refer to these sensory modes of operation as simultaneous (visual) and successive (auditory) processing. Good readers with math trouble show strong auditory skills, but poor visual spatial skills. Reading and writing require a constant alternation between spatial/simultaneous awareness, and temporal / sequential processing.
There is generally good support for the visual therapeutic outcomes for both reading and math trouble. Observations around a child’s sensory dominance and integrative skills can help to direct therapeutic efforts. While necessary, accuracy alone is not sufficient to produce word fluency. Efficient learning proceeds in the direction from accuracy to automaticity, and so therapy needs to address both in balance, and to not overemphasize rote memory and repetition once automaticity has taken hold.
The ‘chair of learning’, then, consists of three legs:
1. Simultaneous / Spatial Processing and Awareness
2. Sequential / Temporal Processing and Awareness
3. Automaticity from Accuracy
Efficiency of integrating simultaneous and sequential sensory demands is critical in fluent reading, and the child’s ability to automatically convert spatial signals to temporal responses, such as through Rapid Automatic Naming (RAN), is a strong indicator of present and future capacity. When the lower order perceptual and sensory-motor skills (proximoception) dominate the child’s performance rather than simply serving as essential background (support services) in the organization of the visual abilities, the child will not develop the expected level of automaticity and may not be ready to learn to read. The child must integrate the temporal with the spatial/gestalt and these are not separable without resulting in a more primitive and proximoceptive response, as opposed to the desired higher-cognitive automated telereceptive sensory and sensory-motor functions. (See http://www.speechlanguage-resources.com/rapid-automatic-naming.html for information on RAN testing, as well as this document – RAN Tx Sample Exercises – for some ideas of how to develop this ability.)
It is possible that a deficit exists in some areas, but not others. The generalization that if motor development is impaired, other areas such as sensory integration will also be affected is not always appropriate or accurate. However, because the sequence and timing of motor skills development are so predictable and because they do frequently reflect the developmental status of other areas of the brain, it is prudent to screen a child for motor developmental status at intake and periodically thereafter. In particular, since visual targeting and fine visuomotor control is predicated on sound gross muscular development, poor ocular motilities is a reliable indicator of a need for work at more primitive levels.
Development proceeds from a state of relative globality and lack of differentiation to a state of increased differentiation, articulation, and hierarchical integration. Children with LD/RD will often show delays in development of hearing, vision, emotional responses, locomotion, motor coordination, and balance skills. Ambiguous laterality (‘sidedness’ with respect to locomotion, preferred hand, foot, eye, and ear) is also more likely in children with learning trouble. In some cases, these children will show very early signs, such as motor delays in suckling and sucking, sitting, and walking – but these signs are neither necessary nor sufficient for an LD/RD outcome.
In normal development, each of these stages of development through interaction with the environment usually provides the child with ‘successive successes, that “I can do it” feeling and reinforcement. Piaget noted that the normal child has had the opportunity that mobility affords to explore and learn about the environment, thus establishing an early relationship between motor activity and perceptual-cognitive development. Among children with LD, the opposite is often true. As mentioned, it is not uncommon to see deficits in speech-motor and visuomotor maturation in this population, and exposure to guided physical and perceptual interaction with the physical environment becomes critical in the early phases of therapy. This approach not only strengthens the neurosensory and neuromuscular foundations of learning, it provides the child with a means to learn success – something very important especially for children who have been ‘beaten down’ by testing, treatment, and derision.
Language ability appears to reside in the hemisphere that controls the side of the body preferred for posturally demanding tasks (‘footedness’) more than the hemisphere that directly controls the side preferred for acts requiring fine motor skills (‘handedness’). Not all individuals who demonstrate unilateral cerebral dominance are good readers, nor are all of those who show mixed or ambiguous hand preference poor readers. Defects of reading, spelling and learning are seldom present in isolation, but are more often part of a more complex developmental syndrome, which includes facets such as anomalies of cerebral dominance and laterality.
Lateral awareness and directionality are perceptual and higher cognitive functions more important to learning than laterality, which is simply a motor sidedness preference. Therapy therefore requires that these be addressed early, before any challenging higher-order skills are learned – the cart must reside behind the horse if the student is to experience success. The proper ordering of therapy also accelerates outcomes by creating natural links between sensory, motor, and cognitive functions.
Motor functions are clearly lateralized for most children, but this is not to say the other hemisphere is silent. Nor does the absence of clear differentiation in laterality mean that a child’s other perceptual and cognitive functions are disturbed. Therapy needs to respect the need to develop the ‘silent’ hemisphere through work with the non-dominant side, but not to develop ambidexterity, but rather because the non-dominant but complementary brain areas provide support and reinforcement to the preferred side.
SID / SPD – The Problem of Integration
An individual with sensory integration dysfunction struggles against the inability to organize sensory information as it comes in through the senses. This condition has been called Sensory Integration Disorder (SID), or Sensory Processing Disorder (SPD).
It would follow that SID / SPD involve not only difficulties with taking in, processing, and integrating perceptual constructs. Given that responses to stimuli depend upon reliable and accurate sensory perception and integration, SID / SPD would also imply difficulties in responding to stimuli in a in a motorically meaningful and accurate way.
For those identified as having SPD, sensory information may be sensed and perceived in a way that is different from most other people, but more likely, the information lacks the same meaning as would integrated multisensory inputs. Furthermore, difficulty processing simultaneous stimuli can mean that inputs are jumbled, frustrating, and even threatening – such as might be the case with autism.
Unlike blindness or deafness, sensory information can be received by people with SPD, the difference is that information is often registered, interpreted and processed differently by the brain. The result can be unusual ways of responding or behaving, finding things harder to do. Difficulties may typically present as difficulties planning and organizing, problems with doing the activities of everyday life (self care, work and leisure activities), and for some with extreme sensitivity, sensory input may result in extreme avoidance of activities, agitation, distress, fear or confusion. In the case of autism, some authors (Simon Baron-Cohen, Mel Kaplan) have proposed complementary models of sensory dysintegration that account for many of the behavioural anomalies commonly observed. Simply put, if the child is subject to constant stimuli in an uncontrolled manner, they will react to protect themselves and will also experience a much higher level of stress on an ongoing basis. The increased shallow and rapid respiratory patterns lead to hypoxia which further reinforces the stress response, further complicating behaviour and management. The overloaded sensory system occurs because they cannot suppress some stimuli or cannot integrate stimuli. This would also explain why IQ measures in ASD are not significantly variant from the general population, and why sensory-motor functions are impaired, such as fine visually-guided movement.
The term SPD is now often used (though not without controversy) instead of the earlier term sensory integration dysfunction that was originally used by A. Jean Ayres as part of her theory that deficits in the processing and interpretation of sensation from the body and the environment could lead to sensorimotor and learning problems in children. Possible a more generally acceptable categorization is that
- Sensory-motor and sensory integration are critical to success in reading and academic learning.
- Rich integrative experiences in the natural world are not available to all children for a variety of endogenous and exogenous reasons.
- Problems in sensorimotor and learning problems arise from deficits in integrative abilities of the child, whether these are environmental (i.e. an impoverished environment), or congenital.
- Therapy that includes activities for multi-modal sensory-motor integration are critical, perhaps more so than any other early therapeutic intervention, even reading practice.
SPD is not recognized in any standard medical manuals such as the ICD-10 or the DSM-IV-TR. The committee that prepares the DSM-5 has requested that additional studies are done before the disorder can be recognized. On the other hand, SPD is in Stanley Greenspan’s Diagnostic Manual for Infancy and Early Childhood and as Regulation Disorders of Sensory Processing part of the The Zero to Three’s Diagnostic Classification. It is more likely that sensory dysintegration appears as a generalized problem on a spectrum with some children affected much more than others. Such dysintegration will also lead to other concerns, such as problems with attention, reading, motor and cognitive behaviour. Addressing disintegrative reading problems with reading practice will most often prove to be plodding and of little use when underlying integrative issues are addressed, beginning with primitive motor needs. Whether sensory processing disorder is a distinct diagnosis or not is not as important as recognizing in therapy that the sensory integrative development is critical in development of higher-cognitive functions and fine coordinated motor skills.
Retained Primitive Reflexes
When a child does not develop more advanced responses to environmental stimuli, they rely on more primitive behaviours. Read this post regarding retained primitive reflexes: http://drboulet.com/retained-primitive-reflexes/