Physiological psychology I
UNIT 1. SENSATION AND PERCEPTION
Sensory informa on is important because it help us to know the world and ourselves through
our senses.
1. Mind, percep on and consciousness
The principal difference is that the behavior is the observable thing that our brain does while the
mind is not observable.
Def. The behavior is an organism’s ac vity in response to external or internal s muli, including
observable ac vi es, introspec vely observable ac vi es, and nonconscious processes.
Def. The mind is the form of behavior not directly observable, thanks to a collec ve of cerebral
processes that influence and are the result of the interac on of the brain and the environment,
conscient (a en on, percep on, memory, language…) or unconscious (implicit memory and
primary emo ons).
Observable, open Voluntary
Motor
explicit
BEHAVIOR Involuntary
Non observable MIND
Most mental processes can be both conscious and unconscious. When they are conscious, they
allow us to no ce our own existence and the world we live, so we can treat them as cogni ve
processes.
The majority of mental processes that are conscious have a big unconscious part, like in the
iceberg. Ex. Language is conscious but some parts of it are not, such as the verb conjuga on.
But can de mind exist without the body or the brain? There is a dualism, there are two reali es
that interact with each other phisic – non-phisic. But there is another opinion, the monism, there
is only one reality. Either is phisic or non-phisic.
1.1 Conscious percep on
Def. Consciousness percep on is when sensory informa on is analyzed, integrated, and
interpreted, based on previous sensory experiences (memory), a en on, context… we could say
that percep on is generated.
The processes that it’s followed to convert sensa on to percep on is:
1. First, we get the s mulus energy, such as smell, a sound, light…
2. Later, the sensory receptors receive the informa on coming from the eyes, ears, nose…
3. Once we got the informa on we get to the neural impulses.
4. Finally, they get to their specific primary areas of the brain (visual, auditory areas…). So,
once they go to their associa on areas so they can get to the thalamus.
Def. We can say that sensa on is the process by which our sensory receptors and nervous system
receive and represent s mulus energies from the environment.
Def. On the other hand, percep on is the process of organizing and interpre ng sensory
informa on, enabling us to recognize meaningful objects and events.
Physiological psychology I
Do our senses deceive us? Do colors, smells, tastes... exist outside us? What is reality?
Our percep ons are influenced by our receptors (perceive a range of energy), but also by
experience, context, a en on... The brain creates the mind (e.g., conscious percep ons) and it
makes us perceive what is going on outside and inside our body. All we know (colours, music...)
exists in our minds because they are created by our brains, they do not exist outside it. Reality is
a construc on of our mind: interpreta on of the brain that fits our sensa ons, expecta ons,
thoughts...
1.2 Consciousness and a en on
Consciousness and a en on are not the same thing, but they do influence each other. You can
be consciousness about something, but you are not paying a en on to it.
The brain creates the mind – conscious percep on – and it makes us perceive what is going on
outside and inside our body. What does not exist in our mind does not exist for us.
Def. Consciousness is a qualita ve and unified subjec ve state of mind (regulated by sensory
percep ons), which brings flexibility to behavior. Consciousness allows us to live mental
processes in an instant, in which everything is perceived as a unified and integrated experience.
Primary Direct experience sensa ons, percep ons, thoughts, memories, images,
consciousness dreams…
Reflec ve Realize the uniqueness as an individual, with the past, present, and future:
consciousness being aware of what we are aware of (self – awareness).
We also must consider the different levels of consciousness that there can be:
Diagnosis Arousal/wakefulness Awareness Communica on
Do not open eyes No evidence None
Coma
No sleep – wake pa ern
Vegeta ve Open eyes No evidence None
state Sleep – wake pa ern
Minimally Open eyes Inconsistent but Ranges from none to
conscious Sleep – wake pa ern reproduc ble inconsistent, but reproduc ble
state evidence
Locked in Open eyes Fully aware Consistent, using ver cal eye
syndrome Sleep – wake pa ern movement
¡The last one men oned is not exactly related to consciousness but we men on it here because it is important.
Consciousness it is useful because it allows us to give integrated and flexible responses. We can
acquire new abili es correct mistakes, decision-making. Allows us to be aware of our own
existence limited by our body. Allows us to be aware that we are aware and that we can think
about our mind and thoughts. Consciousness allows us to live mental processes in an instant, in
which everything is perceived as a unified (integrated) experience and allows the interrela on
with the environment.
Although it is integrated by mul ple micro-consciousness (color, sound...), we don’t feel like we
have more than one consciousness at a me (but as an integrated whole). This allows us to be
aware of what is happening and helps us controlling our thoughts and behavior. "Summary of
reality with an execu ve character“ (Koch) allows quick decision-making
From the integra on of informa on, consciousness allows decisions to be made or acted without
analyzing in detail the perceived situa on (synthe c and immediate): flexible and quick
response.
Physiological psychology I
But how does our brain work so it can make our conscious experiences? There are different
theories that study how it is made:
From the global brain ac vity
From a specific brain structure
From certain neural circuits
a) Role of the brainstem, the thalamus and the cortex
The brainstem arousal systems and the thalamus seem necessary but not enough to generate
consciousness. They maintain consciousness, but they don’t generate it. On the other hand, the
cerebral cortex, and its connec ons to the dorsal brainstem, are essen al for conscious
experience. For example: blindsight, anosognosia…
So, it is important to remember that a en on is not the same as consciousness.
b) Sustained and recurrent ac vity
Consciousness could depend on reverberant ac vity from higher to lower areas of informa on
processing (cortex and thalamus). Consciousness experiences emerges when many neurons
from a dynamic loop of connec ons, this is what we call the dynamic theory of consciousness.
c) Synchrony hypothesis
How can the unity of the conscious percep on be explained? Unified conscious percep on
could occur with the synchroniza on of the ac vity of neurons that process different sensory
features from the same object (i.e., woman) We perceive binding of features.
Simultaneous ac vity of several cor cal areas: Neurons processing the same "object" fire at the
same me and in the same manner (30-70 Hz: gamma waves).
When the thalamus is damaged consciousness disappear. The thalamus and the arousal Systems
of the brainstem maintain ac ve the cerebral cortex and they generate consciousness.
Consciousness is a unified experience generated through connec ons thalamus -cortex
func onal interac on or recurrency (the circuits uncharged of processing informa on work
together, to both sides.
We study the knowledge of neural bases of consciousness and characteriza on the disorders of
consciousness to:
Prognosis (probable course, chance of recovery)
Personaliza on of the most appropriate treatments
2. General principles of sensory informa on processing
2.1 Sensory receptor organ
Def. We can say that sensory receptors organs are specialized cells or neurons that can detect,
respond and transduces a certain form of energy. So, they are involved in the process of
transforming sensory informa on in percep on.
We need to consider that each one of these receptors needs a specific type of adequate s muli.
For example: mechanical, electromagne c, thermal… Each receptor has a restricted range of
responsiveness.
The func on of these receptors is basically transduc on. This means that it converts energy into
the language of the nervous system, electric signals. They can do this once the ac va on
Physiological psychology I
threshold has been reached; the recep ve cells transform the energy of the s mulus to which it
is sensi ve in neural energy (change in the membrane electrical poten al).
2.2 Recep ve field
Def. The recep ve field of a sensory neuron is a par cular region of the sensory space
(periphery, like in the body surface, or the visual field) in which a s mulus will change the firing
of that neuron.
Each sensory receptor is most
sensi ve to s mula on of a specific
area, which defines the receptor’s
recep ve field. When ac on
poten als are elicited from a neuron,
the neuron’s recep ve field codes
the s mulus loca on.
Sensory receptor fields vary in size
and frequently overlap.
Convergence of inputs onto a single
sensory neuron enhances that
neuron’s sensi vity but reduces its
spa al resolu on.
The size of neural recep ve fields
represen ng a given area
determines our capacity to
discriminate s muli in this area.
2.3 Neural coding
There are two ways in which we can represent the s muli in sensory neurons. This process is
called neural coding and is the neural representa on of the features of the s mulus (intensity,
dura on, loca on…)
The frequency of ac on poten als, following not a linear but a power
Temporal
rela onship frequency code
The number of receptors ac vated from low – threshold receptors to high –
Spa al
threshold ones popula on code (range frac ona on)
2.4 Topographic organiza on
Sensory recep ve fields are orderly organized in cor cal sensory areas to form topographical
maps. The loca on of a s mulus is coded according to which group of neurons is ac ve.
Def. Each type of receptor from each part of the body has a dis nct pathway linking its surface
to the brain so different quali es and loca ons of skin simula on can be communicated to
dis nct areas in the brain; these are called labelled lines.
Somatotopic Re notopic Tonotopic
Organiza on of the soma c Organiza on of the visual Organiza on of the auditory
cortex cortex cortex
We interpret ac on poten als differently depending on the pathways along which they travel.
Physiological psychology I
2.5 Sensory adapta on
Def. The sensory adapta on is the peripheral (receptor, not CNS) phenomenon consis ng of a
progressive loss of sensi vity and, consequently, loss of response when s mula on is
maintained. This is why we don’t no ce the pressure of our watch on our wrist; because the
s mula on is constant.
2.6 S mulus dura on
S mulus dura on can be coded by the spike train dura on, but not all sensory receptors can
sustain their responses. The neural code best reflects the change in s mula on, not the steady
state.
Are slowly adap ng receptors
Tonic receptors that respond for the dura on
of a s mulus
Rapidly adapt to a constant
s mulus and turn off. They
Phasic receptors
fire once more when the
s mulus turns off.
